Check out the You're Wrong About on Monica Lewinsky. Even she admits the affair was between two consenting adults. The scandal was not that Clinton abused his power but that he committed adultery (which is legal in all fifty states). Republicans at the time were arguing a man who couldn't keep marital commitments is not fit for office.
Obviously by the time of Trump, they didn't care anymore.
Of all the (many, many) sex scandals in state and federal politics (and coming out of the religious right), The Lewensky affair was incredibly benign. If they have an R next to their name, though, no-one cares.
And then historical Presidents like Kennedy, FDR AND McKinley were far more scandalous.