It's not so much a powerful mythology as it is an objective moral values system backed by divine power. The best book IMO to describe the phenomenon is After Virtue by Alasdair MacIntyre.

I'll paraphrase poorly but basically, MacIntyre argues that when society loses an objective sense of morality that is defined by a force more powerful than any one person, everything begins to breakdown.

Basically, when morality isn't backed by a power greater than man (God or the Gods), each person begins to see their own sense of morality as the objective morality. Everything becomes subjective in this sense. Most people though don't even realize they are doing it. What happens in practice is everyone's reality becomes their own individual "instance" of reality with fewer and fewer shared interpretations of reality among everyone else in society. Because we all aren't raised on the stories of bible or the same mythological stories, people's sense of morality becomes based on nothing more than their own experienced and the content their derive which happens to be considerably more diverse than a shared mythology/religion among people. This then makes it very difficult for people in society to effectively communicate and for a shared understanding of what is right and wrong. This is in part which you can tell two stories to two different people and have them both interpret the story as good or bad in completely different manners. This is why you can tell something to someone and they think that's a good thing or you can tell the same thing to someone else and they think it's a bad thing. Communication itself begins to breakdown because instead of everyone having a shared common understanding of what is right and wrong, people instead resort to arguing the very fundamentals of what is right and wrong. Disagreements no longer becomes disagreements among friends that just have different opinions on how to get to a better outcome. They become disagreements among enemies whose moral value systems are now fundamentalist opposed. Add in a bunch of diversity and inclusion on-top of a culture that doesn't have shared common morality back by a supreme being and you get chaos, more or less.

Unfortunately, it is "leftism" that the government is trying to use as the new objective religion in society but IMO it's failing because this "religion" is fundamentally opposed to nature and so not everyone will accept it despite people wanting to. Leftism isn't a realist ideology based on truth, it's an idealistic ideology being created and utilized to push the interests of those who control the culture of our society. Historically, despite religions being utilized in the same way as leftism, the origins of the religion and mythology were created from a place of real life wisdom and thus still had fundamental truth tied to them despite people trying to use religion and mythology for control. Leftism is a religion developed entirely from the position of controlling others without any regard for truth.