Trump winning Virginia is is based on VA's tendency to support conservative or moderate Democrats in Senate and gubernatorial elections. Trump is unpopular in NoVA, but if the idea of Sanders and 'scary socialism' turns out rural voters in southern Virginia, perhaps Trump could win. This is not something I want to happen, and I agree it is unlikely, but I do question if Sanders is perhaps too left-wing for some conservative and establishment Democrats in the NoVA area, which includes D.C.
But Trump already had high rural turnout in 2016. True, suburban VA wouldn't love Sanders, but that just means he wins it by 3-5, instead of 5-7.