My best guess is a majority of them will end up voting for Trump, but not nearly all of them. I suspect he gets something like 58% of the vote statewide.
He will get 60% easily in Utah in 2020.
His approval rating in the state suggests that is not as easy as you think.
Anectdote, but I, along with many others I know, disapprove of the President. Doesn't mean I won't vote for him.
This is a big part of the reason why I think Trump will win re-election: "I don't approve of him. He's crass and he's crude, but I will vote for him over any Democrat."