Why isn't the rest of the Dai Li investigated after Long Feng is arrested?

The the entirety of the Dai Li are presented to be in on Long Feng's conspiracy yet only Long Feng is arrested? I think that is a huge stretch in believability, that the remaining Dai Li agents are simply allowed to keep operating without any scrutiny from outsiders. I know the Earth King is pretty naive and stupid but no one else within the establishment thought of investigating the the rest of the Dai Li network and that it was enough to simply arrest their leader?

Call it a nit pick if you'd like, but if anyone had the obvious idea to hold the rest of the Dai Li accountable, then Azula can't absorb the agents into her agenda to organize a coup against the Earth King which changes the story significantly. This is a potentially huge plot hole.

If anyone has a possible answer to this that would be great.

Honestly, it feels like there are so many conveniences in this arc of the season that simply give Azula the win.