2018 was a transitional year. The Bills middled 2017. They didn't go all in on a rebuild, they didn't go all in on winning. It worked out and McDermott coached his ass off that year.
It was an odd and risky way to do it. But McDermott clearly wanted his buddy in situ as GM before he tied himself to a Quarterback.
By 2019 they had to win and they did.
He is as good as Stafford, right now. Peak Matt Stafford was a tier above peak Jared Goff. I know he had a good game Sunday, but Stafford isn't still that guy.