I could but it would be a bit of a book. There are books on this. Or youtube videos if you prefer.
There are several concepts here and I am not sure what parts you are missing. Ill just say it again but in more words and you can ask questions. I am a physicist so maybe somebody who has a better understanding can correct some of my errors. There is also a large chance that somebody who reads this is from the far left so maybe they can give their perspective. I’ll give mine as a liberal.
So the western world basically got its ideology in the enlightenment; this can be broadly defined as being a liberal democracy. Befor this it was mercantile and fairly theocratic. Just prior to the world wars there were a few Hegelian based pushes to transform away from some of these aspects. Left Hegelianism through Marx challenged capitalism and lead to communism. Right Hegelianism challenged individualism and led to fascism and nation socialism. Both of these movements were socialist and collectivist but are generally viewed as being on the opposite ends of the spectrum due to their views on hierarchical structures. In any case, both fascism and communism were favoured by the intelligentsia. Fascism and communism have both since been put to the test a number of times and have done a lot more killing of citizens than helping of people.
After the wars some intellectuals from the Frankfurt School came to America. Their thinking combined with the “Critical theory” and postmoderninsm of Derrida and Foucault. The resulting ideology is sometimes called Postmodern Neomarxism but you will know it as the ideology of social justice and political correctness.
Postmodern Neomarxist critical approaches gained influence in the 1980s and 1990s but lost the debate in the public sphere because many common people had a good grasp of the enlightenment theories, particularly those of John Stuart Mill. The people who were Postmodern Neomarxist believers were not persuaded and since many of them were academics they ended up teaching in university. They took up the fields of gender studies, feminism, education, sociology, journalism ect After a generation of teaching this in university instead of liberalism there was enough people in the general public who accepted this ideology for it to start to have power. In about 2015 it reached critical mass. The liberals who had spent the early 2000s making fun of the religious right on the internet suddenly realized that they were no longer the left and the far left no longer just threatened the world with socialism. This changed the political dynamic from being between the Liberals and Conservatives. The Liberals had to switch sides and join the conservatives since they at least had roots in the enlightenment. This shift is going to take a while before things settle.
Does that make sense?
This is a big topic so you are going to need to research it yourself. This is a good article https://areomagazine.com/2017/03/27/how-french-intellectuals-ruined-the-west-postmodernism-and-its-impact-explained/