The incentive is the same with any law enforcement agency, arrests & convictions. The number of arrests & convictions is how all law enforcement agencies are judged; the more you the better you are.
But why this tactic particularly? Why not go after actual dangerous groups?
Are you implying that there aren't enough of these groups to justify their budget, so they have to invent them? This is indeed the obvious conclusion. I was wondering if anyone with more knowledge of the specifics could dream up something more juicy...
It's easier for the FBI to arrest a terrorist that they have been involved with the whole time than to catch a terrorist who is actually hiding from law enforcement.
