Maybe because he has expressed his admiration for Putin on more than one occasion, has sworn to pull all support for NATO, which was founded to defend against a Russian threat, around the time of the election the Russians hacked email accounts of prominent Democrats thus helping Trump’s campaign efforts, or because Trump chose to believe Vladimir Putin over his own intelligence agency in the matter of Russian influence in the 2016 election, Trump’s national security advisor was forced to resign after he had inappropriate contact with Russia to discuss sanctions then lied about it, and because there is a boatload of circumstantial evidence, like relations his family has had with people close to Russia. Maybe for those reasons or it could be people are just really unfair to poor Mr. Trump.