My guess is that it is a combination of all this.

#1. Goff was doing well with McVay babysitting him on the mic at the LOS. He assumed over the next year or so he could take the training wheels off, and they made it to the SB together, big shots in LA, and at the time, all was honkey dorey. So he was ok with the Goff contract. He thought he could make it work.

The rest is a combination of losing some o'line players as well as cooks and Gurley, defenses figuring out the system, and McVay getting conservative with his play calling as well as dumbing it down for Goff.

Now we are stuck with his salary. We aren't necessarily stuck with him.