3 years ago Detroit, Chicago and New England exposed the weaknesses in McVay's offensive system. McVay was slow to adjust and counter the pressure and other teams copied those defensive game plans. Couple that with a Offensive line that lost Saffold and the decline of Gurley and things did not improve and Goff got kind of shell shocked. Goff started playing worse under pressure and teams knew the way to stop the effectiveness of the Rams offense was to get to Goff. Goff has not shown that he can handle the pressure and make the throws. In fact he has shown that he will turn over the ball regularly in pressure situations.
Why hasn't Goff learned how to attack pressure? Certainly he must carry most of the blame for making poor decisions and failing to take the risks necessary to get defenses to back off. But I also have noticed that the game plans seemed to be focused on being conservative, probably to help Goff gains some rhythm early in the game. The offense lacked the punch them in the mouth explosive plays that are needed to put defenses on their heels. Some of that rests on the coaching staff. Goff had a number of QB coaches which may have had some impact also. Finally the HC/QB relationship went sour and in those situations the communications, creativity and trust needed for success had evaporated.
Bottom line Goff was broken and as was his relationship with McVay. If Goff is to be fixed, which is still possible, it would have to be with a new coaching staff so his exit from the organization had to happen if the Rams had hopes for success next year. At the end of the day Goff has to own his decline in performance and his failure to adjust to making great decision under pressure. However, I do think the coaching staff could have increased the probability of Goff successful maturity to better handle pressure.
To bad they crapped the bed on the contract but at the time it looked like he would be the franchise QB and the trend in QB contracts was skyrocketing upwards. But at the end of the day the Rams will be more competitive and the salary cap implications will not hurt the organization long term. The lack of high draft picks will hurt but that is the cost of a great QB while minimizing the cap implications of Goff's contract. .