Yeah, he was. Violence isn't some terrorism related construct invented in 2001.

It wasn't the first time he was breaking the rules though. He was kicked not because of that particular event but because the virtue-signalling potential of kicking him outweighed the benefits of keeping him around once he lost the election. The Capitol attack was just a convenient excuse for kicking a troublemaker that according to their own rules should've been gone long ago.

If Twitter truly cared about their rules and acted with integrity they would've kicked him way sooner, but they didn't because he generated them tons of "growth & engagement" while he was President.

That doesn't make them related.

Trump has made many concrete incitements to violence. Telling his supporters to "rough someone up", "someone should punch that person, I'll pay your legal bills", "maybe some of you second amendment folk can do something about Hillary".