Why not South Lake Carroll - or - Allen.....
Because he's not a seasoned coach. He has very little experience to draw on, other than his relationship with coaches in his career.
He also knows nothing about the local competition, and would be something of an insult to those who have spent more than half of their lives in Texas HS football.
Granted, he's a smart guy and has played at a high level for years, but history is full of ex-stars who failed as coaches. In fact, most top coaches were "scrappers" as players -- guys who were not necessarily expected to excel or dominate, but got by on guts, knowledge, and determination.
I wish him all the best, but his mere presence will not guarantee instant success.