I think the post above has nailed it!
Double bluff – acting dumb means:
A. You’re never asked to do anything challenging or stressful and
B. They will probably promote you away from the front line where you can actually do some damage!
The demand on the resource expands in accordance with the availability of the resource ie if you’re good at what you do and have a work ethic they will just snow you under and you’ll never get promoted as they can’t afford to lose the shire horse.