Monica was not merely a sex fling. She could have become compromised by the Russians, or the Brits or the Israelis. They all would have loved in and out of the Oval Office.
It wasn’t about Monica. Bill could have banged Monica for the entire eight years of his presidency on the seal of the president in the oval office for all I care. It was about Paula Jones. Paula Jones alleged that Clinton had performed certain lewd acts against her. The Clinton team’s position was that Jones was A) Lying B)Crazy and C) a slut and that he would NEVER do those things. The problem was that Monica Lewinsky confirmed that yes, Clinton WOULD do those things (in Lewinsky’s case, she acquiesced), and that she had proof. Furthermore, the Clintons were willing to both commit and suborn perjury to protect themselves.