The otherwise sensible people I know who are still on Twitter all say it's because of a specific interest or group, and the community of people around it who are all on there as well. They all hate what it's become but put up with it because nobody is sure where else to go.
There's also a sense of FOMO when it comes to realtime news updates. Until government, news media, and personalities go somewhere and take all their followers with them, it will be hard to break away.
IRL, arms manufacturers claim they're not culpable when their products are used to blow up civilians. They point at the people making decisions to drop the bombs as the ones responsible, not them.
This legislature tries to get ahead of that argument, by putting reponsibility for downstream harm on the manufacturers instead of their corporate or government customers. Even if the manufacturer moves their munitions plants elsewhere, they're still responsible for the impact if it harms California residents. So the alternative isn't to move your company out of state. It's to stop offering your products in one of the largest economies in the world.
The intent is to make manufacturers stop and put up more guardrails in place instead of blasting ahead, damn the consequences, then going, oops 🤷🏻♂️
There will be intense lobbying with the Governor to get him to veto it. If it does get signed, it'll be interesting to see if it has the intended effect.