Real disillusionment comes after the elite education.
The stuff that crushes your spirit comes later when you go to work at a FAANG and realize that the modern tech sector is fueled not by lofty ideals of innovation and altruistic visions of technological utopia, but by the same cynical profiteering, exploitation and rent-seeking as every other capitalist enterprise.
Your attitude changes once you understand that the high-paying tech sector jobs you spent years of your life training to perform all require you to compromise your beliefs about what is good/fair/just. The jobs require you to build things which hurt people for people who only care about money. Imagine working 40-60 hours a week to make good money doing something you know is at best a complete waste of time and talent.
Real disillusionment comes after you've lived in San Francisco for a while and you realize everyone you know also works in tech and thinks, looks and talks the same way you do and likes the same things you do. And maybe on your way to work at the glossy tech campus that gives you free lunch that your coworkers are always complaining about you pass a tent city littered with needles and human shit.
Eventually you realize that an enormous number of the public figures who went to your university and succeeded in "changing the world" didn't change it for the better. And you may wonder if a lot of the things you've been told about meritocracy and the virtues of intelligence and achievement and wealth accumulation are true at all.