1. Because he is a sociopath
2. Because he can.. and his supporters believe every word or don't care if he is morally corrupt as long as he keeps minorities out of the country and the market keeps going up
Maybe, for the sake of argument, Trump IS a sociopath. He's certainly an asshole, at the very least. But maybe we need an asshole-type to hold the highest office in the US. Look at what that PC milquetoast Justin Trudeau is doing to Canada.
Also, Trump is our President. He's not our spiritual leader. I certainly don't look to him for moral guidance. I look to him to get shit done that's in the best interest of our country. And I think he's doing a great job at that.