- a lot of space that was empty was still under long term commercial leases
- there was less demand to live in some of the cities that had a glut of office space, and especially those neighborhoods
- would a lot of office buildings even make good residential buildings? I don't think this could be a fast or cheap conversion in most cases
This means that it is almost always better to have an empty space than an occupied one that you lowered the rent on--I've seen quite a bit of commercial real estate unoccupied for going on 5+ years now.
This merry-go-round will continue until everything crashes simultaneously.
What would be the point? The residential demand is only there because that's where the offices are.
But the support has no reason to exist without the offices. The offices are the cause, and everything else is the effect.
No, that's wrong. Cities develop for painfully obvious reasons. There are two:
1. The government needs an administrative or military hub and constructs a city to be that hub. This is only moderately sensitive to location, but it involves offices being designated to exist in a particular location and a city growing to support them. Note that there are many, many historical examples of this in which the city came into existence by government decree; it was not necessary for anyone to be living there beforehand. Offices were necessary, and sufficient.
2. Work needs to be done in a particular location. Sea trade happens at a port (and San Francisco is just such a city, though the port is now dead); river trade happens along a river; mining happens at a mineral deposit. This case also involves offices coming into existence and a city growing to support them. But unlike the first case, it's pretty sensitive to location; the hub that supports a port needs to be coastal.
Without the offices, there is no reason for a city to exist at all. Some industries may die and be replaced by other industries that take advantage of the local concentration of people in an existing city. But if every industry dies, which is what eliminating the offices means, the city will die too.
The people at the mineral deposits do not need offices either … they are working in the mines or operating equipment.
The vast majority of people that need offices for work can work almost anywhere.
(Offices are of course required at a mine too, but a comparatively tiny number of them.)