For me at least, it is the lack of fuel efficient vehicles what really did them down.
By fuel efficient, it is of course hybrids, but also in a broader sense, a line of good, economical vehicles.
For instance, a 4-cilinder light duty pickup truck.

The U.S. has reached a point “where the priorities of Congress could become so distorted by politics” that it would turn its back on the next great global industry, clean power — Rhone Resch