They could absolutely do a reduced capacity/mask thing. If indoor restaurants are open, there is no good reason they couldn’t do 20k at arrowhead/BSFS.
Well yeah they could do it but it wouldn't be smart. Haven't been to BSFS in a while but 20k at A's games still leads to a lot larger and tighter crowds than you'd ever see in a typical restaurant because 20 thousand people are all moving and congregating at basically the same times. (I know it's an old shitty stadium but still).
An outbreak at a college or NFL game beyond something like the 85 cases at that Lansing bar would be a PR disaster.
(Also full capacity indoor dining probably isn't the best idea yet, either)
have you seen BSFS when there's 20k people there? Hell, let's call it 17,500, an even third. Require masks. Let families sit together, space everyone else out in every 4th or 5th seat. Encourage people to social distance in bathrooms.
i just don't think there's much of a risk of transmission in that setting -- at least no more than in a restaurant, train station, or city street. i don't think CFB is going to happen anyway, but a reduced capacity situation seems basically harmless to me, relative to everything else that's allowed.