I mean, do you really think the U.S. would have had any interest in a decades-long military campaign against Iraq if the Saudis didn't need protection?
Actually, the Saudis protested vocally against Saddam's removal. The Saudis know that they have US protection - whether they want it or not. Just as the US was not about to let either Hitler or Stalin own continental Europe (the predictable outcome if the US had stayed out of the European theater in WWII), the US will not allow a single power to own the entire Middle East's oil resources, whether that power comes in the form of the Soviet armies, Iran or Iraq. This has nothing to do with Saudi lobbying - it's basic strategy to prevent your adversaries from getting too powerful if their means of doing so is military conquest involving getting a stranglehold on a critical raw material like oil.
It was Bush who wanted to remove Saddam, out of a combination of motivations - I believe the undeclared ones included (1) Saddam tried to have the elder Bush killed, (2) we had unfinished business in Iraq, (3) Saddam may have had a hand in 9/11 that we could not prove, and (4) he never expected the tab to be this big, figuring that it would be a rerun of the Grenada or Panama invasions. It was in Iraq that Americans discovered - contrary to neo-conservative assumptions - inside every Iraqi is not an American struggling to get out. This is why the war has been long and expensive, relative to Bush's original assumptions.
Why didn't the Saudi Royal Family - like every other Sunni-run Arab government - want Saddam removed? Because they feared a democratic Shiite-controlled Iraq would be firmly in Iran's orbit.