The TVTropes Trope Finder is where you can come to ask questions like "Do we have this one?" and "What's the trope about...?" Trying to rediscover a long lost show or other medium but need a little help? Head to Media Finder and try your luck there. Want to propose a new trope? You should be over at You Know, That Thing Where.
If it's done via knocking out the hero with a Tap on the Head, that's Percussive Prevention.
If not for this anchor I'd be dancing between the stars. At least I can try to write better vampire stories than Twilight.I think you are concatenating two separate tropes.
Unfit for Greatness is when a hero or other good character doesn't have the chops for ruling.
I'm not sure if we have one for someone being removed from power for the greater good. Kicked Upstairs is the closest I can think of but that's about being promoted.
Edited by DracMonster
Basically after the end of an arc, the hero has successfully become the head of his company/country/world/[anything with a power structure].
But he's either too much of an idiot or too much of a nice guy, so one of his sidekicks (pr possibly all of them) plot behind his back to take the power, WITHOUT MALICE, simply because they deem the hero incapable of making hard choices, like sacrificing a part of the population to save the rest, or doing shady deals to preserve the stability of the country, or even just vecause they don't want the hero to be involved in something bad that's about to happen...
Basically they just remove the hero from his duties and take the power to protect both the country and the hero, which looks like a huge betrayal but is later revealed to be an extremely loyal decision or for the greater good.
Edited by Uptime