You're discounting the national and racial character of those subjected to the attempted tyranny.

The Chinese for example, and the Germans as another example, are reflexively obedient to perceived authority and often don't question legitimacy either. They are born to be slaves, whatever word you might substitute.

In the United States our problem is different. We distrust authority on general but we're entirely too complacent and too nice, most people assume that the wickedness of the left is a simple political disagreement instead of reason for their eradication. Thus we're unable to deal with infiltrators and subversives, whereas Arab societies would simply shoot them without any concern for niceties.

Who and what they distrust, and to what degree, is one of the key factors in the character of a people.

To answer the title, No. You can have competent or incompetent tyrannical dictators/benevolent leaders so competence doesn't really matter for if they are one or the other.

For the actual thought on the other hand humans can take quite a bit of a beating if they have their basic needs guaranteed to them.

However running a system well doesn't mean that the result of said system is a comfortable life, case and point a system that discriminates against a group can be run competently and it would still make those people miserable.

But you could in theory have a benevolent dictator who simultaneously is tyrannical and gives his people a good life. Some dictators start out as benevolent dictators, gathering all that authority to fix some Illness in their community only to turn into normal dictators once their initial goals is done and that power starts to corrupt them (it's hard sometimes to let go of such a life).

I think the left wouldn't ever be able to keep the people happy with how they treat them even if they ran everything perfectly, discontentment would just grow in people after a while and cause major revolts.

You want to treat people fairly if you want to go tyrannical so that they can become docile, any preferential treatment should be based on what actions a person has done and not on some immutable characteristics they have so that the poor oppressed citizen can direct their efforts into rising up the ladder rather than plotting your downfall.

If a person doesn't have many luxuries because they aren't working hard they will be easier to control than if they don't have luxuries due to skin color for example. Unfairness due to immutable traits leads to growing discontentment which will then make people question why their life is so oppressed (which the dictator doesn't want)

What differentiates the often-benevolent monarchies of the past from modern tyrants is a culture of indifference or even contempt for the governed. Monarchies and similar systems in traditional societies were built on the concept of noblesse oblige wherein future monarchs and the children of the aristocracy were inculcated with the idea that their rights and privileges came with a responsibility and a duty of care for those who owed them fealty. They didn't always take that concept to heart, but many of them really did, and that produced a sort of reciprocal loyalty between the aristocracy and the governed.

The modern elite were born out of the new liberal middle class of the industrial revolution. They did not inherit and were never educated with that same sense of reciprocal duty in mind, and their inherent materialism predisposed them to think of human beinfs as just another resource to harvest in order to enrich themselves. It is possible that some of their poor governance decisions are the result of incompetence, but I really think that for the most part they both hate the rest of us and are terrified of us. They can't ignore the possibility that some of the middle class might be able to supplant them, because they themselves are a product of exactly that.

Is the main reason why the left is slowly losing every gain they make or attempts to copy authoritarian rule similar to others down to simple lack of basic competency?

It's the aristocratic tendency to promote their retarded, inbred progeny over competent, meritocratic outsiders so power stays within the clan. Not even Marcus Aurelius, philosopher king and the last Five Good Emperors of Rome, was immune to this.

Then there's generational differences. The First generation builds the wealth, the Second grows it, and the Third are spoiled shits that don't know how to maintain it. Everything usually falls apart after three generations for this reason.

I suspect this is a large part of why Boomers are clinging to their office seats all the way to rigor mortis. The alternative is to put their dipshit children like Justin Trudeau Castro in charge and destroy their decades-long legacy, and that terrifies them.

I should clarify, when I said 'Benevolent leader' was being a bit tongue in cheek as I was referring to leaders who massacred their population but were still highly regarded afterwards and took programs of de-indoctrination to even dent the reverence. I see how that can be misinterpreted.

China has gone through several dynasties. The end usually looks like what we see now.

Incompetence has to reach a certain level before it is fought against. Ludwig III had several castles and buildings in his honor before the people and military revolted against him. The French revolution was started by upper class folks who thought they could just control the mobs. China went through 3-4 leaderships last century and we don't talk about it. So the incompetent need to pass an insane level first. I thought it was happening during Covid, but I was wrong.

Orientation with the Good, or Natural Law, or Moral Law, or however you want to put it.

My main issue with our overlords isn't that they're incompetent: it's that they're Evil. If anything, incompetence is a feature since it keeps them from being as effective at carrying out their Evil.

The line is ethnic association.

is the line between tyrannical dictatorship and benevolent leadership competency?

There's plenty of overlap but, no, it's not a defining characteristic.

Competency and motive. You can have extremely competent dictators who are good at being tyrannical, or you could have competent dictators who are good at facilitating prosperity for their subjects. The latter are very rare, but do exist. The problem is they don't last, and their power inevitably gets transferred to either an idiot or a power hungry tyrant, often times both.

Gonna buck the trend and say Yes actually. And I have proof in a place called Singapore. They have a private healthcare system yet have a public purse for medical procedures. They're a dictatorship, yet the country is run profit first with a high standard of living. They have 3 major racial groups, being Chinese, Thai and Indo-asians yet because of subsidized government housing, they're all forced to collectively come together to be known as Singaporeans. In the video for instance, they recently had one of the lowest percentages of approval for the ruling party, it's not an election rather a census measuring how popular they are every time the cycle comes around. Competent leadership results in high numbers, while corruption and inefficiency results in low numbers, but not enough to oust them.

Singapore is of course an outlier. They're rich enough to actually afford socialist programs, which is how the ruling party stays in power. Meanwhile in the west, they have to resort to growing tyranny in order to hold a grip on power and prop up failing social programs by just printing money.

The Chinese are probably horrified by the authoritarian system in the West, where you cannot even call a man a man. Most of the 'social credit score' of the Chinese system is simple anti-social behavior that everyone opposes. This is quite unlike the kind of behavior the Western countries crack down on, which is normally the opinion and attitude of the vast majority of people in their "democracies".