Comment by beerandt

Conflicting interests between how much they disagree with him politically and how much money they directly make off of his traffic (and less directly via traffic from everyone complaining about the controversy).

Twitter's business model is totally reliant on controversy. They want to treat/control, but not cure/extinguish.

Which is a separate reason that twitter's ethically conflicted in making almost any judgment calls on what's "allowable" speech.

Additionally, the nature of mud-slinging politics requires that ones opponents "follow" his online presence in able to attack. So if Trump leaves Twitter, not only do his followers go to whatever new platform he does, but so must his adversaries.

Twitter doesn't want that.