I'm also willing to bet the personal attacks are kept to a bare minimum at Mastadon, where as with Twitter, you just have be idk...opposed to one popular political thing publicly to be regularly attacked and harassed.
How much of that is just because there aren't as many people there though? Both in the lack of enough people to make a critical storm of people and just not enough people to form an audience for that kind of action. I doubt that would remain the same if Mastodon took off and became a huge thing.