Firstly, he wasn't living in a cave. Secondly, you do realise how far his terrorist network stretched ? It wouldn't have been JUST him that planned it any more than it was Bush and Blair that planned the tactical side of the invasion of Iraq.
Of course you're allowed to question things .... just don't claim things as fact because a few crackpots have put up YouTube videos without any hard evidence.
No, at the time UK troops possibly wouldn't have gone to Afghanistan if 9/11 hadn't happened but that doesn't provide evidence that the American establishment carried out 9/11. Of course the ruling elite can and will manipulate a horrible event to their own means ( remember the phase "a good day...
They didn't need to do that to justify invasions. Anyway, it's an utterly ridiculous argument. Such a conspiracy would required dozens, possibly hundreds, of people to pull it off. It just wouldn't be possible to keep that many people quiet for so long.
I'll answer that after you answer the question already put to you ...... WHY would the American establishment have done what you claim ? What was their motive ? What was their purpose ? If they did do it what have they achieved ?