Norwich probably had the best squad in the Championship thanks to the fact that they retained most of their good players when they were relegated. They're returning to the Premier league thanks to, not because of, the new manager. They had a great start to the season but were sliding rapidly down the division until Alex Neil arrived.
The right manager is the more critical part of the equation; Bournemouth achieved promotion with a great manager and a run-of-the-mill squad, Norwich are promoted with a great manager who turned a very good squad around.
Exactly, they, Norwich, retained their best players. Can you think of a club that didn't?