Those polls are meaningless 14 months ahead of the general election. Trump is a highly polarizing figure who (a) will also almost certainly not win the nomination and (b) is widely hated enough that he would likely lose head-to-head against a ham sandwich. The other Republican candidates don't have hardly any name recognition because Trump is monopolizing all the media attention.

I'm not sure how much elaboration you need for the idea that an avowed socialist wouldn't be elected President of the United States.