Santorum should read what Bush's own 9/11 Commission says.
From Chapter 2 of the 9/11 Commission Report:
It is the story of eccentric and violent ideas sprouting in the fertile ground of political and social turmoil. It is the story of an organization poised to seize its historical moment. How did Bin Ladin-with his call for the indiscriminate killing of Americans-win thousands of followers and some degree of approval from millions more?
The history, culture, and body of beliefs from which Bin Ladin has shaped and spread his message are largely unknown to many Americans. Seizing on symbols of Islam's past greatness, he promises to restore pride to people who consider themselves the victims of successive foreign masters. He uses cultural and religious allusions to the holy Qur'an and some of its interpreters. He appeals to people disoriented by cyclonic change as they confront modernity and globalization. His rhetoric selectively draws from multiple sources-Islam, history, and the region's political and economic malaise. He also stresses grievances against the United States widely shared in the Muslim world. He inveighed against the presence of U.S. troops in Saudi Arabia, the home of Islam's holiest sites. He spoke of the suffering of the Iraqi people as a result of sanctions imposed after the Gulf War, and he protested U.S. support of Israel.
Many Americans have wondered, "Why do 'they' hate us?" Some also ask, "What can we do to stop these attacks?"
Bin Ladin and al Qaeda have given answers to both these questions. To the first, they say that America had attacked Islam; America is responsible for all conflicts involving Muslims. Thus Americans are blamed when Israelis fight with Palestinians, when Russians fight with Chechens, when Indians fight with Kashmiri Muslims, and when the Philippine government fights ethnic Muslims in its southern islands. America is also held responsible for the governments of Muslim countries, derided by al Qaeda as "your agents." Bin Ladin has stated flatly, "Our fight against these governments is not separate from our fight against you." These charges found a ready audience among millions of Arabs and Muslims angry at the United States because of issues ranging from Iraq to Palestine to America's support for their countries' repressive rulers.
Also read my college paper about our relations with Iran.