I feel like with boomers it had a lot to do with them being the wealthiest generation in history. Wealthy boomers did a lot of class warfare against literally everyone else, and after it started impacting peoples lives significantly that’s when the anti-boomer stuff became common.

Which in a way kind of sucks because it ignored that there were plenty of poor boomers, and leftist boomers. It also distracted from the fact that it was a class issue, making it easy for it to just be co-opted by the right later into generational warfare.

No war but the class war stays true once again.