I think this is really just more of a question of how silly polls can be years before the election. There were multiple national polls showing Hillary ahead of all Republicans by 20+ points.
Yep, and we'll probably see a lot more outrageous polls the next time one side or the other has an inevitable nominee. The reason why Hillary had such a big lead against certain republicans is there are a lot of people who will say before a primary, "well I don't see how I could stomach voting for x", and tell a pollster they're undecided or even voting for the dem or a third party. But after the primary, when push comes to shove and they actually have to vote against their party, they almost never actually do so.