I'm in no way blaming Clinton for 9-11. However, there were several previous terrorist attacks against the US (1993 WTC, military housing in Saudi Arabia, the embassy bombings, and the USS Cole, to name a few) by Al Queda during Clinton's Administration. In each case, if he took any military action at all (and he didn't after the WTC and the USS Cole attacks), it was to lob a bunch of cruise missiles into mostly empty training camps. Bin Laden saw this as a sign of weakness and was emboldened to bigger, more terrible attacks. He said as much on some of his video messages.

Could they have killed bin Laden in 2000 using aiming data provided by that Predator? Part of it depends on when they first mounted Hellfire missiles on Predator UAVs. The CIA certainly had them in operation in late 2001 but I don't know if that capability was available when the video was taken in 2000. If they did, then they could've taken the shot immediately with a high probability of success. If not, they could've used the Predator to keep the suspect in sight and called in an air attack with fighters or cruise missiles.

When Clinton spoke of "bringing them to justice", he was speaking as a lawyer with the naive idea of arresting terrorists and bringing them to trial. In the real world, that is a pretty rare event, especially when you don't use military forces to capture them in the first place. After his shameful reaction to the 19 Army Rangers being killed in Somalia, Clinton was so risk adverse against casualties that it was hard to get him to take any sort of effective military action. Case in point was the use of force in the Balkans. They wouldn't let the attack planes go in at less than 15,000 feet. As a result, pilots dropped a lot of bombs on decoys and more civilians were killed due to less accurate bombing.