"Donald Trump is the first president in history whose campaign has come under F. B. I.-initiated investigation for collusion with a hostile foreign power. And the person heading that investigation, the F. B. I. director, has been fired." (Timothy Egan, NYT Op-Ed, 11 May 2017)
It might help if you read Rosenstein's Comey memorandum and related documents here. But if you are a lefty, it probably won't.