Much good information already.
I think the key is size. A power station generator is huge and will fly apart if spun too fast. Aircraft generators are much smaller and can be turned faster without disintegrating. Generators are usually turned as fast as they can tolerate because that means more power.
The generator's frequency is now almost irrelevant because the frequency can be efficiently and cheaply changed with modern electronics. Generate whatever frequency you want and feed it into the magic box, nice clean 400Hz (or whatever suits) comes out. Traditionally aircraft alternators (generators) used constant speed drives, but newer installations are able to dispense with these heavy and complex devices.
"
A VFG on a A350 (Variable Freq Generator) ranges from 360Hz to 800Hz (idle to takeoff)"
If a piece of equipment can deal with this, e.g. a heater, it gets a direct feed, otherwise electronically altered to DC or 400Hz AC as required.
https://en.wikipedia.org/wiki/Constant_speed_drive
https://aviation.stackexchange.com/q...-ac-generators