The disastrous first season (ie. the last gasp of Jeff Fisher) is a part of the story as well - what little he played, he was awful in that first year on an absolutely awful team. And, iirc, he was largely treated like crap by that coaching staff and lost a ton of confidence as a result. And that more than anything else really set up McVey to kinda look like the guy who "made" Goff - people went from writing him off as a bust to declaring that McVey had "fixed" Goff in a matter of months.
The 1/1 thing is a factor as well, but there are some unique circumstances in Goff's background which have kinda led to the perceptions imo. It's a complicated story, but the reality is that while McVey deserves a lot of credit, Goff is a good QB in this league and, only now it seems, is he starting to get more of a benefit of the doubt.