It was both his policies and his attitude.
1. Do you remember how he fired people who told him the truth; i.e. Paul O'Neill was ousted from Treasury for warning about deficits. Larry Lindsey was kicked out of the top White House economic job for predicting in 2002 that the Iraq war would cost $100 billion to $200 billion.
2. Returning to deficit spending. The federal government was running a surplus when he took office.
3. Tax cuts for the rich. The time was right when Reagan did this, but times change and Bush's cuts made the coming disaster much worse. Part of the blame does have to go to Reagan, Bush and Clinton. But G. did not help mantters. The economic conditions when Bush took office were almost opposite to those when Reagan took office.
4. Lack of financial regulation. Here also Reagan, Bush and Clinton share blame.
5. Just like presidents before him he had no energy policy in attempting to lessen our dependence on foreigh oil.
6. The Iraq war that deepened our debt, especially to the Chinese.
7. Neither Bush nor Obama took the bailout far enough. Interestingly the Chinese have read our economic textbooks. When they saw the trouble the instituted a very huge bailout program and now their economy is moving upward very nicely ... for them, not for us.
Unfortuantely for Bush many of the problems that had been growing for years were not addressed by his administration and they blew up before he left office. Now, if I were really cynical, I would say he knew the problems were there and he could leave office before the train really wrecked. I do not know if this is true or not. But the bottom line is his administration did not address the problems and now we are in a mess.