>dude can commit all sorts of crimes and as long as Congress
>doesn't impeach him he can just get away with shit?


Yes and no.


There is no precedent if a sitting president can be indicted. Mueller can indict Trump (while still president) if he sees fit, but Trump would ultimately take the indictment to court. The case would make its way to the Supreme Court where it would be decided (if Kavanaugh is confirmed the Supreme Court would probably rule in Trumps favor). Avoiding a long drawn out legal battle it would be easier to just start with the impeachment process in the House of Representatives.

Nixon would have been impeached because he lost the confidence of the Republican Party, so instead he resigned to get out in front of the situation and not be disgraced by the impeachment process.

Trump hasn't lost the confidence of the Republican Party (he ultimately is the Republican Party) so that's why we are in this current predicament. Members of Congress, who are afraid to go against Trump (fear of reprisal, so to speak), that's where the problem lies.

If we had a "normal" Congress, things would probably play a lot differently.