Collaboration is risky. If it fails, if the occupation is wound up prematurely and the bad guys come back to power, you might find yourself in some serious trouble.
Niall FergusonAll empires have depended on local legitimacy and local collaboration; they are not based primarily on coercion. An imperial rule that relies wholly on coercion can't endure. It's too expensive.
Niall FergusonEmpires, essentially, create order. In their absence, you don't end up with lots of happy, little nation-states full of people sitting around campfires singing John Lennon's "Imagine." What you end up with is civil war, anarchy.
Niall Ferguson