No, it was a response to white fears stoked by years of GOP dog whistling, which you should recognize by bringing up immigration. Immigration isn't a hot button topic because Dems want to talk about it. That perceived economic loss isn't because Dems publicize it.Did he? Or was all that a response to "white privelege", intersectional politics, and a perceived economic loss due to open borders that left an opening on that topic with economically distressed white voters?
You are perceiving their reaction through your lense. They perceived that with a Democratic focus on race issues, their concerns were getting ignored. They went to someone who talked about them. Same reason blacks tend to congregate in one party. They feel that party talked to their concerns. White people are human too, they act no different than anyone else.
The GOP has been playing with fire in order to get out the vote for years. Trump is just the racist chickens coming home to roost.