Yeah, ever heard of something called "Watergate"?
watergate is not (for me) a very important thing.
He lies? So what ? All politics lied, and spy rivals is not a nixon exclusivity. (in France, mitterrand as spy-listened more than 1000 peoples)
It might not be important to you, but to the American people, it was damn important and still remains a marring piece of his legacy.
It wasn't like one of those "I promised to do this during the campaign and didn't do it while in office". I'm unfamiliar at best with the intricacies of Watergate, but as opposed to things that went on with JFK and LBJ where things were found out years after their Presidencies and not very much cared about, this was smack in the middle of his Presidency and forced him to resign.