Same schools, same boards, same vacation spots, same parties, etc. Same ideas about how the world works. The class delineation is quite clear. Yes, there is a lot of variation and rising "counter-elites", but why exactly should we ignore the elephant in the room?
A giant driver for the massive deconstruction of class privelage was exactly an unrelenting obsession by bystanders, to claim that any and all adverse results are due to "the elite decided this" .. so -- to be on the Board of any of those companies is generally speaking an end-result of 25 solid years of competitive situations, where some people "win" .. the Board directors are MORE exploitive and aggressive precisely because they will be replaced with others that will do it. I utterly disagree that there is some insider track in the USA that results from where you went to kindergarten or who you spend vacations with..
The elite verifiably did get behind "the end of history" narrative, and their opinions matter because they have a global megaphone in the form of the mainstream media.
It's not some grand conspiracy of rich people plotting in a dark room. It is the common interest of an extremely influential class.