I also know it took enormous pressure to get the Obama administration to agree to act (along with NATO) in Libya, and then ONLY when time had all but run out. That's not exactly the profile of a nation (or government) bound and determined to protect its vital economic "interests" exclusively.
There are more currents, deep currents, at play here than just "black gold." The West had a stable oil partner in Gaddafi, a partner more than willing to provide a steady flow at a reasonable price. There was no reason to upset the apple cart for oil.
Yes, there are more currents involved which we know nothing about.
However, just as a note, I know quite a few Libyans and they told me the US had forces in Libya on the ground from the start. They had the impression that the US was deliberately intervening in a very slow way, almost as if they were taking the time to get to know the factions involved in overthrowing Gadaffi.
The overwhelming feeling from the Libyans I was talking to was that the US was concerned about replacing Gadaffi with a government which would be extremely hostile to US interests such as a radical Islamic government.
Therefore, my Libyan friends told me they believed the US slowed down their assistance to the rebels until they could figure out which factions were pro-US and anti-US. I think this is quite a sensible approach and my Arabic friends surprisingly agreed with that. Even more surprisingly, the French 'diplomats' I met in the region believe this is US policy but believe it is intelligent as well. This was a first - the French agreeing with US policy...