Imagine Donald Trump putting his hands over his ears, closing his eyes firmly and shouting "Lalala, I'm not listening!". That is more or less what he is doing right now. He used to grip for a straw that is no longer there: "I'm not under investigation". His favorite comforting mantra now seems to be "Nobody has found any evidence". That, however, is most likely wrong.
Donald Trump does not seem to understand how a criminal investigation works. When proof or circumstantial evidence is found, you don't announce it to the world and to the suspects. You keep it under cover and dig for more until your case is solid enough to press charges. It's very likely that several people in the White House are facing serious charges over various crimes, but the hammer won't fall just yet. We can rest assured, though, that the various investigators have found a lot more than rumors, or else the probes would have ended long ago.