Not even his supporters today knew if they were going to vote for him back then.

This is completely false, I have no idea where you’re getting this idea. Trump was extremely popular with conservatives in the 2016 election, and conservative voters are famous for toeing the party line even when they don’t like the candidate, so even if they didn’t like him they all knew they’d still be voting for him. There was absolutely no question at all on if his supporters were going to vote for him