I was thinking of this with that: Horst Bendix invention: Tower construction for a wind turbine - the tower rotates and the generator is in the tower base
I think for a belt or rope drive the generator needs to fixed relative to the rotor, so this makes that possible.
Right this moment I can’t picture if using a shaft is possible also when the rotor and generator do rotate relative to each other. If it is, putting the generator at ground level was perhaps always a possibility, but I imagine a belt or rope drive makes more sense.