And going beyond just money, remember that the Saudis went after one of the richest businessmen in the US (Amazon's Bezos), you can expect they also went after other businessmen and politicians, many of whom are a lot less tech savvy and protected. That's a lot of things potentially held over important people's heads.
In that context what you are saying makes no sense.
That turned out well don't you think? Iraq was a historical enemy whereas Saudi Arabia is a key ally of the United States. This alone should give you the feeling that there's something happening behind the curtains to justify such an alliance with a... controversial country.
Before that, in the 70s it was a Baathist secular dictatorship that was an oil exporter and thus reliant on the US dollar, while Iran was a Kingdom with a US puppet as Shah.
Going from ally straight to enemy and war is probably a big step even for the US.