I'm thinking it was a combination of #3 and #4, but I went for #4 since that was the final straw. Griese was handling the QB duties decently (like Dilfer on the '00 Ravens decent
) as the defense was keeping the other team from scoring as much as the offense could.
Once Simms got in there, and combined with the loss of their new star RB, I'm sure the offense was deflated. There's no way they should have lost to the 49ers 15-10. They should have beaten the Jets also (14-12 loss). With those victories in hand, they're 7-1 right now and on top in a very tough division.
Sure, Carolina and ATL could have beaten them down later and knocked them out at a later date...but at 7-1, the Bucs would surely feel better than they might right now at 5-3 and 1-3 in their last four games.
Simms is going to have to muster some sort of respectable pass game, or else teams will just stack the box against the run game and score enough to win every time. It's not over yet, obviously...but the chances of them beating ATL or CAR right now aren't looking so good.