What they really mean is that it has given them their greatest sense of purpose. Education is often dry, a bit boring, and doesn't necessarily provide anyhow with a great sense of purpose in life (take a social science research methods class and I challenge you to say it lit a moral fire in your soul).
But the problem with finding a sense of purpose, especially when you're doing it in a mass setting, as a participatory act with others, is that you may not actually be learning. Yes, you'll hear moving moral claims, and certain empirical claims that may be accurate (or might not), but what you will not encounter is critical debate and discussion - group think will prevail. There will be an appearance of debate and discussion, because there will be much talk of issues and ideas, but active debate, questioning doubt, and disagreement, will be actively discouraged and suppressed.
So real learning cannot take place, only indoctrination. But it feels good. Students get a sense of being part of something noble and of great moral importance. It will be a high water mark in the lives of many of them. But will it provide them any lasting value beyond memories? Not likely. It's certainly not teaching them to think (but, mostly, neither do their classes, most studies show), and it doesn't teach them the value of listening or having any sense of moral humility. Instead it encourages an absolutist moral certitude, a refusal to listen to disagreement, and a belief that small groups making demands is proper way to coordinate and negotiate social outcomes.
People cheer them only because they agree with them. If this was done by any group with which they had substantial ideological disagreement, there'd be no smug congratulatory articles in the leftist press (but there would be in the rightist press!). Instead, there'd be outage at their gall in daring to do exactly the same things these young leftists are doing.