My memories are fairly vague, but I do remember the "Pool's closed" raid leading to some random grandmother getting flooded with phone calls from /b/tards.

The Chris Chan saga also started in 2007, from what I just looked up.

There was definitely a gradual decline, but it was happening even back in the 00s.

I think it’s gotten worse, especially after GamerGate led to people tasting political power, but I think “reserved” was never completely true - even in the 2000s it had the same reputation for leaking unpleasantly. Mobs are simply volatile.

It's likely not the same people but instead a slow culture shift as new people come in and push the limits a little bit more. There's also a feedback loop as the more extreme actions will drive out less extreme users and attract more extreme users.