Note that the rim pulley is attached to he hub with spokes.
I am sick and tired of dealing with chain drives! Testing special chain lube, replacing the chain every three months or so.
But this has got to have it's problems also. Like the belt has to be too tight, and the bearings wearing out fast. and the dirt wearing out the cogs. Gates has a CenterTrack variant that supposedly runs at lower tension than their original style. And carbon fiber costs way too much! better to use a belt drive for a motor.