It's worth separating two goals
1. I don't want to hear Donald Trump, and I don't want to associate with anyone who likes him, or hear their ideas in my feed: this is solvable by distributed systems like Mastodon where node operators can just blacklist the Trump-aligned servers, and apply rules on their own.
2. I want Donald Trump to be silenced and not be able to say dangerous inflammatory things that rile his supporters up into violent attacks on democratic processes: this is going to require a centralized decision and really probably would work best if it was a law.
Deplatforming can partially work by demanding all reasonable node operators block the person. But then you get the ones whose niche is to be a haven of scum and villainy, like Gab, and they refuse.
This may be enough, though, if it isolates awful people into inaccessible backwaters.