It's a key thing to keep in mind when considering his actions. He can rile people up in directions they're already leaning... He hasn't really demonstrated much ability to lean people in any particular novel direction, or against their pre-existing biases. He'll provide a focus to existing anger and say things that people don't want to say out loud, but he's as much a component of the overall anti-authoritarian, anti-establishment political wing as a leader of it.
Clarification: some of his supporters.
And how did he encourage the vaccines? We didn't have daily tweets saying things like 'TERRIBLE people opposing vaccines! SO SAD!!' He didn't really get behind them.
You can't spend four years supporting everything that undermines them, and then quietly say 'get vaccinated'.
It was indeed quite an accomplishment.
What was unexpected and ironic is what came afterwards, where opponents of the administration quickly got vaccinated in large numbers and supporters of the administration did not. There are some interesting graphs here [1].
Lately Trump was been pretty vocal about telling his supporters to get vaccinated, and even that doesn't seem to be changing many minds.
[1] https://www.npr.org/sections/health-shots/2021/12/05/1059828...