Why are large air conditioners so delicate?

A couple things could be going on. Power failures in general should not be the cause of total equipment failure and more often will cause electrical issues that should only require electrical components to have to be replaced not the whole unit.

Roof top units should last 10+ years with proper maintenance. My guess would be the units are either old and just are finally conking out and need to be replaced and you have to remember they were all new at the same time so it will be a daisy chain of failures as once one goes the rest are not too far behind. The other possible reason is they have not been maintained. Changing the filters and belts at least once once a year and twice a year lubing of the drive shafts is minimum for our roof tops.

Since you mentioned “so susceptible to being damaged when losing power?” I’m thinking you might have a power feed problem. It is worth checking.

Electric motors are susceptible to burnout if they do not receive the electrical power they require. Make sure you have 220 or 440 Volts supply when the motor is running. If the wires are undersized yo might not be getting enough which causes the motor to overheat.

If the failures are the control electronics, I’d invest in a good UPS large enough to keep the controllers supplied with clean power during drop outs or power failures.

In my experience, office buildings with broken air conditioners are usually suffering from broken fan blowers, or from mismanagement of the air flow (janitors responding to requests to cut or increase flow, then going overboard).