You're missing the point. It's not that they're gullible, it's that one side ignores them completely and the other side is speaking to them. It doesn't matter that the guy telling you what you want to hear is probably lying, its still a better spot than the guy that ignores you because they don't want or need your vote.

It’s amazing how many people in the left still don’t get this. Trump supporters absolutely did not vote for him out of gullibility. They got exactly what they expected.