This deep appeal of Trump by about 30% of the population is "interesting", to me. The more radical stuff he says, they more they like him. I think it's not issue related, it's more about how they think he's going to "hit back" and shake things up and really do stuff by not being a politician.
The immigration thing obviously is a big part, but another part is shaking things up in DC, somehow, and oil drilling (even though we're at record levels now).