Real question is though, which is the cause and which is the effect?

• Is the cause that, previously a bit more sophisticated, leftism became dominant and now it's a bunch of mediocrities coasting on rusty versions of those ideas?
• Is the cause that leftist ideas are more intuitively appealing vs more sophisticated moralities entirely dependent on abstract reasoning and non-obvious/intuitive dynamics? And thus being the harder road inclines people to go "eh fuck it I'll take the simple sugar coated option" [also see the end about why you'd make people dumber...]

While both aspects contribute, I think the latter is more prominent and fits with historical development; it has NEVER been 'obvious' to believe in individual rights and that a complex system where individuals can pursue their own interests yields a better outcome for more people than other systems...

The intuitive idea is just the "right/smart/whatever people" being "in charge" to micromanage the design to try and achieve the "obviously desirable" means AND ends - be it at the level of a tribe or into the autocracies of today.

Which is another reason leftism is so infested in education and seeks to undermine REAL learning; they know, probably not explicitly but implicitly from interactions with those who disagree with them in life, that they don't have sophisticated ideas that hold up to scrutiny...so they undermine the ability of as many people as possible to scrutinize their ideas, and ideally brainwash them into buying into them by getting them young.