Why shouldn’t they celebrate? Not only did they win in Afghanistan but 9/11 turns out to be a striking success for them. Muslim immigration since 2001 to the US has increased to such a point that viscerally anti American Muslim politicians are elected to Congress,they have the MSM and Academia fawning over them and protecting them, and have huge political influence. 9/11 resulted in a mass example of the Stockholm syndrome.
Islam’s goal has been to “breed out” the infidels and take over. The are working on Europe and America. They are much smarter than any democrat in the US.