I think there are several things driving this, not necessarily generational:
Many employers (not the tech industry) enjoyed a weak labor market for roughly 2 decades. And each time when things began to heat up a recession would come by and cool things down - flooding the market with newly unemployed qualified candidates.
This sustained discrepancy caused many employers "people management" skills to atrophy. Treating employees badly was OK because 1) Where else are they going to go? 2) Even if they quit you can just hire someone else who is likely just as qualified. Because of this, anti-social behavior among management never seemed to impact the bottom line, so it became embedded into the culture of these businesses - "That's how we've always done things here!"
Things changed sharply in 2020. You had the pressure of Baby Boomers retiring. And unlike other generations, many Boomers actually saved for retirement; employers did not have the power to retain them. Second, COVID pulled a ton of people out of the workforce for several reasons: needing to provide childcare, death, "long COVID", etc all pulled people permanently or semi-permanently out of the labor pool. At the same time, consumer spending shifted placing additional demand on many industries that were now shorthanded (and short-supplied).
The problem is many of these companies do not have the ability to attract and retain employees. On your local news you might've heard a sob story of a local employer having to cut hours or close-up shop because they "can't find anyone wiling to work" - but if you dig a little deeper you'll find they have a reputation in the community for being a bad employer. People do want to work - just not for them. And because there's no longer a cushion of qualified labor that has to settle for their anti-social work environment, they can't hire anyone to operate their business due to their poor reputation among the local workforce.
If you're young, your first step into the labor market is likely going to be one where you're asked to pull double-duty by an organization that, again, has a poor reputation. Their first experience in the workforce isn't at some friendly company, but rather a hostile employer who drove experienced labor away, forcing them to "settle" for someone with no work history. Thus giving these young workers probably the worst (modern) experience possible of what it means to be in the workforce. Thus the aggressive job-hopping - it's not a candidate problem it's a company problem.
So how does this get fixed? Well, if the labor market stays hot long enough, many of the anti-social companies will just get out-competed by ones able to attract and retain skilled labor. In this situation the rising tide will NOT being lifting all boats.