There's no point wondering what Devers might have or not have done, there's no point looking at his numbers and transporting them directly to if he'd stayed here. We don't know anywhere near enough of the variables. The trade might have rocked him, he might be have issues settling in SF (SF media certainly hasn't taken to him), he might have personal issues, it might just be a down year, he might hate the limelight that's come his way after the event, or a whole myriad of other reasons.
The problem with making absolutely every argument stat base is that we forget human beings play this game not numbers.
That said, I have always been happy we've gotten out of that contract as it's certain it will go bad at some point, and I hated his attitude throughout the whole debacle.
But we all boil these things down to numbers far too much.