Restaurants have always had a difficult business model. 26%+ fail in the first year. 60% fail in the first three years. Even the profitable ones run 2-6% pre-tax margin. Re-opening with customer density limitations and higher food costs will be even more difficult.
SF has its own business environment issues, but this story and associated document makes for an interesting read:
https://sf.eater.com/2020/5/13/21257567/architects-coronavirus-seth-boor-tartine-dear-inga-delfina