As head of Al Quaida, Bin Laden has his own constituency, his own following. He wanted to look good to them, to look powerful, the kind of man who could pull off such an act. Just like Kim W Un in Korea wants to look like he's not going to let the US push him around.
As for hiding, well everyone on both sides know the US Govt. has much better war-making capabilities and that killing Bin Laden would be a high priority (at least at first). What would you have expected him to do?
It was nothing but the typical bravado of a child immensely pleased with a newly acquired skill, like a successful potty-training session. "Look what I did, Mommy! Look what I did! " Sometimes, children shouldn't brag about the things they have done wrong. Someone might be listening. And, they might get punished.
He was proud of 911. It was a powerful blow that weakened his enemies, and raised his importance in the eyes of his fellow Jihadists.
He hid so that he could continue to operate for as long as possible without being captured or killed by his enemies.
Tapes were found in a cave of him admitting it.
No
if he was just going to hide why would he admit that he planned the bombing
