Osama bin Laden was the infamous leader of the terrorist organization Al-Qaeda, and for quite some time he was the most wanted man on the planet.
He formed the organization because he was not fond of the idea that the Muslim world and the Western world should have close connections, as he though that the West has made a lot of terrible things to the Muslim world.
He used his enormous wealth, the constant flow of money by oil, the extremist fractions, as well as the large quantities of weapons that the United States delivered to the Taliban during the Afghan resistance against the Soviets.
All of those things set up a fertile soil for the development and expansion of the terrorist organization which was responsible for lot of attacks and deaths, mostly of innocent people.