You're probably right that some members of the staff last year didn't want to draft a QB... There were rumors that the Rams were split on who to take, Snead wanted one QB Fisher wanted the other.. Well apparently Snead won that argument, hence why he's still here and Fisher isn't. That would actually explain why Fisher refused to play Goff or set him up to succeed, he did the exact same thing in Tennessee when they drafted Vince Young against Fisher's wishes.
But that was last year and we don't have that staff anymore other than Snead, Fassel, and some lower guys that don't have much influence, so I don't think they're that worried about the Goff pick. McVay could have opened it up to a competition, in fact early on he signaled he was open to it (you jumped all over that I believe).... And then he spent more time with them and Goff was named the starter early on, and that's been the end of that. It's pretty likely that McVay evaluated both of them while he was getting settled in and going up and down the roster (as was his job) and he knew who he wanted. If he wasn't sold on Goff that was the time to make a change, this year is the year for him to try someone else. If he's not trying someone else then that should say who he liked more. The fact that a few weeks ago we heard that the Rams weren't happy with any of their QB depth behind Goff, if that's true, says what McVay thinks. It could be simply that Mannion isn't a scheme fit, he's someone that was billed as being perfect for a run heavy offense, a good game manager that can get into a rhythm and do some good things, perfect for that Fisher offense (and I think he was a Fisher pick)... McVay is running a different offense that needs a different type of QB. Look at the three QB's on the roster... You have Goff, a pocket passer who can excel in a pass heavy offense... Orlsovsky a (bad) pocket passer that is comfortable in a pass heavy offense (Connecticut ran a spread offense when he was there), and Mannion a game manager that can excel in a run heavy offense. He's got skills, which is why he's our backup, but McVay might not see him as a scheme fit, but without any other alternatives, he'd rather him than someone else backing up Goff.
Goff isn't starting due to politics or the team not wanting to embarrass themselves (we fired Fisher in the middle of the season last year, we're past that point), he's starting because he's the best QB on the roster.