Question about Al Quaeda?

When Osama Bin Laden was fighting with Russia, USA came to his aid and supplied him with training, arms & ammunition. But now, OBL is against USA and sending terrorists to kill American nationals in the name of Jihad. Why would someone someone consider us an enemy, when we helped them sometime ago? Is the government holding back some sensitive information from the general public, which is the reason OBL has turned against us? My Muslim friends have confirmed that the Quran(Koran) says nothing about Jihad, so why are these people not using their minds??