Is if they think Stafford is done/about done. Do they think that? It's possible. We don't know the medical reports they are privy to. But I think it is unlikely because Stafford has been getting hurt for years, the guy has hard miles and they knew that when they paid him.
I do think it's probable that not being able to financially make Mayfield work got McVay thinking about who's up next. Because I think he really enjoyed working with Mayfield. And the losing reset his realities wrt his QB depth chart, as evidenced by the immediate purge of his entire QB depth chart. But even with those two things I don't think QB that early makes sense.
I would rather have Hall in round 4 than Hooker in round 2. I don't think Hooker along with concerns of that knee injury is that much better than the other options and there's more than one with Hall, Haener, Tune, etc. He's a better QB prospect certainly but if we pick him he's gonna sit the bench. So weighing everything it feels smarter to draft one of those backup QBs midrounds and be more efficient in using your draft capital.