I hate when people make it sound like being a GM of a football team is easy. There is a lot more to it than just signing, trading and drafting. You gotta overlook the cap, manage contracts, scout players, hire the correct staff, build a solid relationship with said staff, create healthy relations with players and agents, and many more things. And while GMs have a lot of people working with them (scouts, Assistant GMs, etc), any sort of personnel decision or transaction, good or bad, will fall onto them (for the most part). So whilst I love Peyton Manning (GOAT), thinking that he would do a better job at managing this football club than Grigson is just absurd.
and btw, not saying Grigson is a good GM, and not saying Peyton CAN'T be a good GM. Just that this idea, at this point, is beyond asinine