There is another theory I've heard that I like:

1. The parents of the millenials were the boomers. The parents of gen z was gen X. Millenials and boomers are fairly equally disliked, and gen alpha seems to be shaping up to follow that trend.
2. If you have been paying attention to legitimate complaints about each generation, you'll notice similarities between the kids and their parents. Both millenials and boomers get hate for being terrible parents and workaholics, and the hate gen z is currently getting for having no work ethic sounds very similar to the hate gen X got back when they were in their 20s for being supposedly lazy and stupid becuase of MTV.
3. This implies that we are seeing not one pendulum of overractions to generational trauma, but two. The Millenials and the Baby Boomers, if you trace it back, descended from the humbly named Greatest Generation which fought in WWII and set the wheels of modern American culture into their current tracks. Gen Z and Gen X descend from the Silent Generation, who were best known for being conformist and pretty much nothing else.

Here's the conjecture part of the theory: the Boomer lineage has been taught that what matters is what you do and if you don't achieve you have no value, whereas the Silent Generation lineage has been taught that good people are good to their family and community and being a workaholic is bad for that. The poop-throwing you're seeing online is simply an expression of a conflict between opposing values.