OL is so easy to find that we've managed not to put premium resources into the OL since drafting brick and Mangold in 06. How's that worked out?
The problem here is asset allocation, anyway. If you draft a QB at the top of the draft then either Sam or that QB is a wasted pick. You can't have both of them on the field at the same time, and the odds are pretty good that whoever you put on the field will be playing behind a very subpar line yet again. Because, well, take a look at who the upcoming free agents are. It's not a pretty list on the o-line - and some portion of those won't hit free agency in the first place. For the ones who do, other teams will be bidding on them and we aren't exactly the most attractive free agent destination right now.
So we need to invest in the offensive line with our premium picks. Doing so maximizes both the value of our big free-agent acquisition this offseason, in Bell, and gives our current key asset, darnold, the best chance to reache his upside and be the franchise quarterback we've needed for decades. My point is that even if darnold fails, and you have to move on from him, spending those picks on the offensive line isn't a waste, because it provides a foundation the next time we are in position to draft a QB. And if darnold flops, we will be in a position to draft a QB, because our team will not be good enough without him to be not drafting in the top 10 next year as well