Just like today ... we all know that because of our unsecured southern border another -- likely even bigger -- attack is coming ... we just don't know when or where.
I'm reluctant to lump Donald Trump in with the "Truthers" who believe the U.S. Government was a party to 9-11 ... that's not what Trump said at all ... it's just an inference by those who want to take down Trump.
The resentment is not that Bush let it happen - he did not correct the root cause of the error - immigration.
Pearl Harbor was FDR's "mistake" but the nation forgave him that because of how he handled the fight back to Japan. Bush gave us an Iraq war that never ends and seems to have made things worse and not better.
What I wrote above is my interpretation of Joe Six Pack's perception of Bush around of the events of 9/11 and after.