One of the problems is - there are multiple teams desperate for a franchise QB who are drafting far higher than the Rams. And you and others are acting like Goff is a sure thing - not a good prospect, but a sure thing - and it is silly to think that the Browns and especially the 49ers wouldn't have noticed him, if that were the case.
Now, as I've said before, I have doubts about any college QB who doesn't take snaps under center. It's not that it's hard to teach him to catch the snap, it's that the reads are radically different, especially for a QB who routinely has 4 WRs to throw to, instead of having a system where Gurley is the focus. Historically even "sure things" have trouble adjusting at times to that change.