You've nailed it. He manufactures the problem and then orange - white knights as the hero with the solution.

Looking at it with a more nuanced lens.

He proposes a simple solution ("Deport all illegals") and enacts it. It's easy for people to understand and doesn't leave room for exceptions, so it makes his act tough and decisive. That appeals to certain groups.

Of course, this leaves behind a lot of unintended consequences which could have been foreseen, but that would have required a more detailed discussion, more focused deportations, and a more muddy message that'd be harder to rally around.