Closed primaries: there are lots of ancestral Democrats, Dixiecrats & otherwise federal R voters locked into voting D because of party reg, particularly in western NC. It's the same reason he did so well in WV, KY, OK, etc.
WNC ain't like WV, OK, or KY. Those are real granola eating birkenstock wearing people until you get past Jackson Co. Buncombe is pretty liberal on every level now and there are wealthy retirees south of there. Plus many of he mountain counties have a R history and the Ds are really D. The housing is pretty expensive (and not in trailer parks) and the rate of college degree attainment is pretty high.
Yes and no. That's true of southwestern NC to a far greater extent than the NW part. Ashe, Alleghany, Avery, Mitchell, Yancey counties are as redneck as anywhere in West V. It's really the Brevard-Hendersonville-Asheville-Boone corridor that is heavy on Yankee retirees and hippies.