Taliban and Al Qaeda had been at each other throats especially post 9/11. There has never been love lost between them. It had been personal decision of Mullah Omar to put islamic solidarity over realpolitik.

Some clever policymaking - mixing military threats with financial incentive - could result in catching most of Al Qaeda possibly Bin-Laden included and avoid 16 year war. But B-1 coming with vengeance after mountain caves looked better on TV and as propaganda spin post 9/11.