Like Cheney or hate him, he kept the country safe for the better part of 8 years.
There is no proof that anybodys policies had anything to do with preventing another 9/11. Since there had not been one before with no Cheney policy.
But there is the logic that certainly had to do with preventing them. (1) Now that passengers knew that terrorist would use airplanes on suicide missions, terrorist would have a much harder time executing and being successful against an attacking group of passengers as in the Pennsylvania Crash group. (2) Had the Pilot training schools reported the suspicious trainee request, such as only training for takeoff. (3) Had the pilots that had scrambled to intercept these planes been more coordinated. (4) Had the towers used some architecture technique that would not pancake as they did. All of these coincidently combined to give these two-bit terrorist the look of giant killers.
And then the Bush/Cheney bunch started beating the war drums, throwing a war on the wrong country (Afganistan - Bin Laden), using a lie as an excuse to go in (Weapons of Mass Destruction), using the liberation of Iraquis as an excuse for being there (ridding of Saddam Hussein), and in general starting a overblown, unaffordable, worldwide war on terror that will go on forever. This is a virtual dream come true for a fascist and a bottomless money pit for our country.