The reason US intelligence is often wrong is because it relies too much on satellite imagery and electronics intelligence (eavesdropping from a distant). This kind of information is extremely subjective — you can interpret it any way you want. The really good intelligence is gotten through a network of personal contacts that are on the ground and understand the nuances and intricacies of the local culture, language, and history. Because of its over reliance on technology, US intelligence has gotten lazy and superficial — things are never as black and white as it paints them, particularly not in the Middle East.
Add to this the fact that US intelligence is often manipulated and corrupted by politicians to meet their own (and their party’s) agendas and respond to their fears and suspicions. Intelligence gathering is no longer dominated by the cultivation of relationships. It has been taken over by photos and recordings. That’s why the US got Iraq totally wrong, and that’s probably why it may be getting Syria totally wrong. Who pays for these infantile errors? US military personnel and hundreds of thousands of innocent civilians. Oh yeah, US taxpayers. George W. Bush? He’s retired and living a comfortable life in Texas.