So they got him.
Why was he so "popular"? I think it was his smile.
Bin Laden always smiled. This was his unique selling point. Most photos of extremists show either a hateful scowl, emotionless resolve, or at best a forced, unfriendly smile.
Bin Laden smiled, but it wasn't an evil smile. It looked perfectly genuine. He wasn't smiling because he'd just killed lots of enemies. He was just calm and content with being a killer. At peace. His videos illustrate this most dramatically. He was collected, quiet, almost shy. I've seen more passionate performances by college chemistry lecturers.
That was surely his appeal. No-one joins a movement like Al Qaeda unless they're angry, but Bin Laden seemed to be living proof that you didn't have to stay angry to stay a member. Al Qaeda was the way out of that. Al Qaeda could bring you inner peace. Whether Bin Laden was really like that, I have no idea. He might have been tormented by inner doubts, and just good at acting for the cameras. The point is, it doesn't matter. The images were out there, and that was the message.
His calm was also the reason why he was hated and feared more than the other members of his organization, including the ones who had a more direct role in 9/11. Osama was the one man to whom the image of the ranting, delusional extremist couldn't apply. Someone who planned terrorist attacks out of insane rage: that would be bad enough, but at least it would be understandable. That someone could do it with an agreeable smile on their face, was something else.
Given which, it's no surprise that the U.S. reported that Osama died a coward, hiding behind his wife. Nothing could have shattered the Osama image better than that. He wasn't beyond human emotion after all, he was scared just like anyone else. Again, whether or not that actually happened, is not the point. It's the message that went out, and I suspect that's the message that will stick.