The way I see it, the trade only makes sense if you assume that Detroit wanted Goff. Otherwise why not take Bridgewater and Carolina's 8th pick.
Holmes knew Goff, he was part of the personnel team that drafted him. He was present for all 5 of Goff's years. You have to assume that Holmes was acting as a conscientious GM who was doing what he thought was best for the Lions. He must think he is set at qb with Goff. That fits my view, I always thought he could rebound from the problems of 2020.
On the other side, if Stafford lives up to his billing (and you have to think he will) then the trade justifies itself. I am one of those who thinks that Stafford is the Archie Manning of this generation. Put him in a good spot, with a running game and a defense and team that does not have awful morale issues, and he ought to be one of the league's top stand-out qbs. I know about the gun-slinger, "massive mistakes now and then" issues with Stafford, but I always wondered if that came from pressing to win in bad situations.
Though the amount he gets banged up and plays banged up, while it speaks well of his toughness, makes me think that the Rams need to keep investing in the OL. None of this is secret. Whitworth is not getting younger, there's well-known issues with the interior and a center will help, and I don't think they have a complete OL really until they upgrade from Hav. Not all of that has to be done at once, but the OL needs to be a continuing project. I suspect I am not alone in thinking that.