In his case, he depends on it and so does the media in analyzing his tweets. That would be an interesting scenario where he loses a channel he considers as important outlet.

People don't give the guy enough credit. Whether intentionally or accidentally he developed a strategy that hasn't been beaten yet. If Democrats in America don't realize this, he's going to win 2020, too.

If Twitter shut down, he'd have a HUGE say in which platform would be its replacement. MILLIONS of people (both left and right) would start accounts to follow him. Honestly, I can't think of another celebrity for whom that would be true.