Because none of those annexations haven't affected "core" territories of the west or their "core" population. The west definitely did not ignore 9/11.
Some people are more "western" than others. More specifically, the ones that can vote to mobilize the "western" military. Spill their blood and get demolished. Spill the blood of their worshipers and suddenly their own blood is too valuable to waste.
9/11 was an used as an excuse for pre-planned actions again unrelated entities. The US made huge efforts to avoid responding to the actual attackers for almost a decade.
Some people are more "western" than others. More specifically, the ones that can vote to mobilize the "western" military. Spill their blood and get demolished. Spill the blood of their worshipers and suddenly their own blood is too valuable to waste.