> Maybe I'm naive, but it seems pretty obvious that it's because technology is mostly full of leftists, so they tolerate their own extremists and ban their opponents. Deplatforming has been a tactic of the left for a while now.

I wouldn't say that technology is full of actual "leftists", more a group ranging from overly-myopic liberals who struggle to do what would actually benefit minority communities in a more positive sense to the libertarian types who only end up restricting what people say because it ends up affecting their advertising revenue. Simply by virtue of being in a position of financial power, it's very difficult to hold truly leftist views.

>Deplatforming has been a tactic of the left for a while now.

Deplatforming has been the go to method of the right for at least a century (see mccarthyism) and longer if you include lynching/death as essentially equivalent (ie: you can't speak if you're dead). The left has simply finally got enough critical mass to do it themselves.