Getting fired from a job is a serious harm, especially because having your reputation shattered in this way makes future employers reluctant to hire you, since the same people will have no scruples about turning on them. We're talking about devastating life impact here. I don't think you should trivialize this as "what nobodies on Twitter are saying".
They're not being killed, of course, but I think the word destroy isn't out of proportion for having one's livelihood and reputation ruined. Otherwise you could just as easily say "Who is getting destroyed? Being put in prison for a little while is not being destroyed." That would be the natural next step, after all.
Again, if someone was fired from their job, that's their bosses prerogative. Plus, the list of people who haven't gotten work again perceptually due to "cancel culture" is hard to enumerate. Roseanne, Louie CK, Kevin Hart, etc. have all worked since they were "destroyed". Neither their livelihoods nor reputations are ruined. Hell, listen to Roseanne's interview with Joe Rogan right after her ABC cancelled the reboot. He tried his hardest into leading her into blaming "cancel culture" for her problems, but she responds that she's doing fine, living in Hawaii, near where her son goes to college and she (still) owns a Macadamia farm and has a tour lined up. That is far from a "destroyed" life.
The people who have been in prison (Cosby, Weinstein) might have had a different outcome, but that's because they were arrested and placed on trial, which is a function of the legal system, again, not the work of angry tweeters. If you're saying the justice system is at the whims of "cancel culture", you're just being silly.
That doesn't change the point that for most people getting fired from a job is serious life damage that ought not to be trivialized as "angry tweeters". A few outlier examples don't prove otherwise, losing a TV show isn't the same thing, etc. It seems to me that you're minimizing the significance of this development. There's also the fact that ostracization is traumatic for most people.
What I said about prisons was unclear, sorry. I was trying to imagine what the next escalatory step would be after getting someone fired. Perhaps it would be putting them in prison. If so, someone would be making the same argument again: it's not as if their life was destroyed just because a few angry tweeters got them jailed, they'll get out soon enough, and so on. The point is that there are degrees of harm. Just because it could be worse does not prove that harm isn't severe.
They're not being killed, of course, but I think the word destroy isn't out of proportion for having one's livelihood and reputation ruined. Otherwise you could just as easily say "Who is getting destroyed? Being put in prison for a little while is not being destroyed." That would be the natural next step, after all.