He was never coming back on Sunday Night Football, against the undefended biggest Cowboys rival, and with the team 4-0 without him. There would just be too much pressure for him to play well and too much risk that he doesn't against the Eagles on national TV. Then you'd have to hear "but Cooper Rush led the team to 4-0 and now Dak looks horrible and we lost"!
He'd much prefer Rush look bad and we lose (So far it's looking good for Dak there), so he can come back against the worst defense in the NFL next week instead.
Dak Prescott, the patient, would be an idiot to start without giving his throwing hand the recommended time to heal.
Mike McCarthy, the head coach, would be an idiot to start Prescott with a throwing hand that is still iffy.
Jerry Jones, the owner/GM, is just an idiot.
Idiots make stupid decisions. Luckily, those three were not idiots. At least not this particular week.