That's not just incorrect, but dangerous thinking, because it makes it too easy to underestimate the enemy. Germany and Italy in the '30s were fine places for the citizens who weren't being murdered, with thriving economies and military innovations far beyond the rest of Europe. Osama is clearly evil, but he's been shrewd enough to organize attacks all over the world and elude capture.
And even in countries with evil leaders and great human suffering, the leaders manage to keep themselves in power and their cronies in luxury. Their people suffer not because the leaders are too dumb to figure it out, but because they don't care.
It is necessary to recognize both evil and ineptitude in leaders, but it's dangerous to assume they go hand-in-hand. That makes it too easy to blow off the threat posed by a 7-foot-tall madman who defends a 14th-century version of theology and lives in a cave.