From I Drew This:
Clinton's outgoing national security team warned Bush's incoming National Security Adviser, Condoleezza Rice, that she was going to spend most of her time dealing with terrorism and Osama bin Laden. She did nothing to act on this advice, possibly because "do the opposite of what Clinton did" was the major ideological creed of the incoming administration.
In March of that year, the bipartisan Hart-Rudman study was issued, which argued that America was likely to face a large-scale terrorist attack in the near future and recommended some steps to protect against it (many of which, had they been in place, stood at least a chance of doing something to thwart 9/11). Bush ignored the report, and instead had Vice President Cheney convene an antiterror "task force" to come up with its own set of recommendations.
As of 9/11, Cheney's task force had never met. But it's not because Cheney didn't have the time for task forces; his energy task force met a bunch of times during the same period. The administration just didn't take the threat of terrorism seriously. Clearly, Gary Hart and Warren Rudman did. As had the previous administration.
But the Bush Administration dropped the ball. Even that infamous August 6, 2001, national security briefing, titled "Bin Laden Determined To Strike Inside the United States," failed to raise any alarm bells or rouse Bush from pretending to be a cowboy on his "ranch."
- Presidential Daily Briefing, 2001-08-06: bin Ladin Determined to Strike in US (declassified 2004-04-10)