There was a theory in 2004, known as GIFT: Normal Person + Anonymity + Audience = Total Fuckwad
Guess what? People without anonymity are total fuckwads too - this happens on Facebook, Instagram and Twitch, in an era where you could probably find someone's personal details if you look hard enough.
I think the key is audience. Bullying feels good for a lot of people. Bullies will go for low hanging fruit where they won't be struck back.
You see people acting this way even in once helpful sites like Stack Overflow; downvotes will pull bullies in like a magnet. You see people picking on anti-vax, flat earthers, Justin Bieber, not so much because they do harm, but because they're easy targets to hold down.
Viral algorithms amplify this effect. It highlights bad news that everyone can join in and rage on. It's not a new thing; news channels have done this for decades.
We can't really fix it. I'm more a community nomad these days. It's easy to move on to other new and old communities, away from this effect. I've been happy with HN, Discord, and IRC lately.. IRC has picked up back to 500 people per channel, and it's probably no coincidence.