During his 2016 campaign, Trump asked Russia to release Hillary Clinton's emails. As president, he met with Putin in secrecy with no other officials present and went as far as destroying the interpreter's notes. These are a few prominent examples of his utterly bizarre behavior towards Russia.

I'm inclined to believe Trump is simply stupid and admires Putin as the kind of strongman he desperately wanted to be, but he certainly stoked the theories with his own behavior.