It doesn’t matter why the republican base believes in their party. Incidentally, you’re not entirely wrong about why, but they’ve had rebellion too: see the TEA party.

The democrat party strategy is different. Their base isn’t aggrieved axe-grinders. They’re earnest believers in the system. The problem is that the leadership doesn’t actually want to accomplish anything that would threaten corporate profits. Trump is great for them, since all they have to do is not be him! Policies be damned.