Toyota's and Honda's troubles seem to bear out the assestions made over the years that F1 is a tougher nut to crack than CART, etc. Each of them stumbled early here, and went on to crush Ford and Chevy, albiet as engine suppliers only. MB's one-off domination at Indy told a similar tale.
Honda and Toyota seem to supply mighty powerfull motors, it's the rest of the package and the team issues that trip them up.