It seems unlikely that a commercial real estate crash wouldn't have second-order effects on residential. After all, if none of this commercial space is getting used, there is less of a reason to be interesting in the residential housing that surrounds said commercial space.
Depends on what is meant by "commercial". If we're talking about retail and restaurants and bars, then sure, the loss of those things will make it less attractive to live in/near those locations.
But if we're talking about office buildings, and the reason for the collapse is because people don't need/want offices at all (not because those offices are moving elsewhere), then I think it'll have a much smaller effect on the residential markets.
What I think has a higher chance of hurting residential markets would be hiring moving away from HCoL areas because companies believe that most workers can be remote (and workers in LCoL areas are cheaper comp-wise). That hiring movement already seems to be happening, though SF home prices haven't changed much. There might just be a delayed response to that, though.
We're seeing a shift in demand across different sectors of the real estate market, not a destruction in demand. The market for office space is cratering, as is the market for 1BR apts/condos in dense urban cores. But most of the people who would've occupied those buildings are still working, they're just working from home. The market for SFHs (particularly large suburban ones with home offices) is exploding. I'm seeing some in Mountain View and the SF peninsula go for ~$350-500K (up to 15-18%) over asking.
