Osama bin Laden and al Qaeda didn't just pop up on our radar when 9/11 occurred.
They were increasingly stepping up both his actions and his rhetoric in the following 8 years.
In 1998, Bill Clinton was very aware of the terror training camps in Afghanistan, and was very aware that their goal was to attack the US homeland and other US/western interests, but he was afraid to take any kind of real action, mostly fearing a popularity backlash.
Keep in mind that Clinton spent much of 1998 embroiled in the Lewinsky scandal, so he didn't want to give people further reason to hate him. Popularity was always Clinton's biggest motivation. I always said that Clinton cared too much about public perception, and GW Bush cared too little.
In August 1998, Clinton ordered rockets fired at al Qaeda bases in Afghanistan. These were a failure. The rockets caused some moderate damage and a few casualties, but they did not take out any al Qaeda leadership, nor did they scare al Qaeda or disrupt their operation.
After this, Clinton ceased in his attempts to thwart al Qaeda, which emboldened them further. This resulted in the October, 2000 attack on the USS Cole.
Regarding 9/11, bin Laden reportedly said during the planning phases, "All they'll do in response is fire a few rockets at us again", wrongly assuming that the US wasn't willing to take any major action against their organization, even after the most major and deadly terror attacks on US soil.
When going through old videotapes, I actually found the beginning of a 1998 news broadcast where it was stated that bin Laden was announcing "a major attack on the US homeland within the next 5 years". So this was widely known and reported, and still Clinton took no action in the final 3 years of his Presidency.
Clinton was also aware of al Qaeda sleeper cells within the US after the 2000 Millennium attack plans were thwarted. He was criticized in a repors by the 9/11 Commission for his inaction during his final year of Presidency, despite being aware of these cells.
Clinton was so upset about this report that he sent his buddy Sandy Berger into the National Archives to steal documents related to it in 2003. Berger was caught, and admitted that he stole these documents related to Clinton. However, he claimed that he did this on his own, and that Clinton had no knowledge of it (lol). It was also eventually revealed that Berger had unsupervised access to "classified files of original, uncopied, uninventoried documents on terrorism", and could have easily destroyed a lot more than what was actually discovered and proven. Berger died in 2015, still a very close friend of both Clintons, who made a phony denouncement of him at the time he was originally caught.
Bush wasn't perfect regarding 9/11, either. He was handed a report in August 2001 that an attack by al Qaeda on the US homeland was "imminent", yet took no action.
Still, we're talking about a month's time here, whereas Clinton let al Qaeda run wild for years.