It's called generating your own problems. Yes, the gas guzzlers were selling well, but even in those years, it was known that the price of gas was bound to go up dramatically. They were just not proactive enough. If they had been, they would have been ready with small, efficient cars ready to be put on the market the moment the gas prices had gone up.
However, it's wrong to say that the gas guzzlers were the only problem. GM cars have basically been abysmal since 1980. Apart from a few exception, everything they made from 1980 to present time have turned out to be awful products. The only reason they kept the corp. aloft during that time is that they relied a lot on patriotism of the American people that want to buy American cars.
If I was going to buy an American car, I'd turn to Ford, which, while still having made poor decisions in the past decade, was the first of the big three to see the light, and start actually changing things. These days, there's nothing shameful about buying a Ford over a Toyota, and if I was facing the dilemma of buying a Fusion (2010) or a Camry, I don't know what I would do. Besides, they have the Fiesta coming over soon, which apart from apparently being a good car, is really good looking, both things American cars have been lacking for a while.