OBL is not a "true believer", he is one who has hijacked an otherwise legitimate religion just for his own perverse advancement. If anyone is naive, it's you.
History disagrees with your assessment of Islam.
"True believer" or not, he and his minions are the roots of this pestilence and the keys to exterminating it.
Why he, his training camps, and the Jihadist schools have not long since been annihilated is beyond my ken.
You'll have to ask Mr. Stangegov for that answer.