Lindsey Buckingham and Stevie Nicks had a band before they joined Fleetwood Mac in 1974. It was called "Buckingham Nicks," and I may be one of the few people in the entire world who actually saw them play live in 1973, when their album was released.
If you could hear this obscure record, which included the subsequent Fleetwood Mac hit, Crystal, you would see that Fleetwood Mac needed them more than they needed Fleetwood Mac. In fact, from seeing some personal portrayals of the members of Fleetwood Mac, sans Buckingham and Nicks, I would have to think that their combined IQ's would not be that of an average living room light bulb.
They were obviously a band looking for a brain.