Why do new seasons start in the fall anyway? Other than tradition? I assume that there had been a reason at some point. Why not start new seasons in January?
The sound stages and all other resources are booked by the off season shows that also have to be made.
All the new shows have to play together in a cluster to keep the ad revenue even between the Networks, and avoid a slaughter.
Something about selling new shows to the affiliates at a convention.