There were unethical Presidents FAR before Nixon.
Look up the Teapot Dome Scandal during Harding's term. Also, even way back in U.S. Grant's administration, his whole staff was pretty corrupt and he was ignorant of it all. Andrew Johnson was impeached way before Clinton. Lost or forgiven because of his assassination were plenty of shady happenings in the Kennedy administration.
Anytime anyone has that much power in any time in history, the temptation and opportunity to be corrupt exists.
Nixon was just not good at getting away with it.
