Interesting. It's not that I don't believe you but every source I've read on this issue seems to have such an ideological slant that I don't know what to believe. The Wikipedia article changes dramatically every time I read it. It once stated quite emphatically that criticisms of the conspiracy theory came primarily from libertarians and other conservatives.

The PBS documentary Taken for a Ride takes the position that it was a conspiracy (perhaps not in LA) nationwide.

I still don't understand why GM et al would feel the need to buy these systems out if they were already in such severe decline. If the national trend was already away from transit, why would GM feel the need to buy out the transit systems?

And this kind of skirts the broader issue of GM's influence on that national trend. They lobbied for the urban freeways, the intercity highways, the mandatory parking, etc. They ran national ad campaigns touting the freedom of the automobile and asking people to lobby for more and bigger highways. It's not as though the trend away from transit happened independent of other factors.

Edit: So to me it seems only rational that a company inherently interested in selling automobiles would want to make its competition (transit) as unappealing and inconvenient as possible. Buses are noisy, they pollute, they're bumpy, and they don't come with any infrastructure making it less obvious when they do disappear.