Are you sure about that? I was sure about that ("there's no way Trump can win") last election, and I was utterly wrong.
As far as his chances of winning - I personally did see had a fair shot in 2016, because the issues he was talking about mattered to a lot of people that had been disempowered over the past 8 years. I personally believe in LGBT rights, but it was obvious that there was going to be a horrid backlash from the gloating of projecting a rainbow on the White House. But since being elected Trump has addressed very little of what he campaigned on - the swamp has been further packed, and he's basically golfing and shitposting instead of leading. At this point he's coasting on favorable propaganda from Faux news, and the middle of the country will have that illusion shattered as we blow past 200k deaths.