Poverty is of course a huge problem and a huge issue, but any proposed causative link between poverty and terrorism is strained at best. And while it's easy to point to poverty as a problem, it's a good deal harder to do anything about it. Development aid simply doesn't work. It doesn't win hearts and minds, it doesn't have much impact on poverty, and it certainly doesn't do anything about terrorism. It allows donors to feel good about themselves and say nice things about themselves, and it keeps the aid industry afloat, so you can say it's doing what it's intended to do... but let's not pretend that it's doing anything abut poverty.
You are wrong. Most terrorists are poor.

To access the Western World you must be both financially stable and educated. So the terrorists that attack the West tend to be middle class. On the other hand, most terrorist activity in the developing World (where the majority of terrorist activity occurs anyway) is carried out by poor people. Nigeria's first suicide bomber was a roadside mechanic and suicide bombers in Iraq, Pakistan and Afghanistan tend to be poor.

Finally, Osama bin Laden's flavour of Islam is not the traditional Islam of the merchant class, it is the Islam of desperate young men from slums. That it was co-opted by the middle class does not change its primary audience.

It all boils down to poverty.