The Bush administration invaded Afghanistan to take out the Taliban. It did, but the mission -- guess what -- was not accomplished. The Taliban staged a major comeback. Now the Obama administration is more or less inviting them to come back to power.
Pentagon hardliners could not possibly live with the idea of Washington abandoning Kabul in a remix of Saigon 1975 -- helicopters flying away from the roof of the US embassy. The Obama administration wants at least to save some face. Practitioners of Full Spectrum Dominance want their bases. It ain't over till the last Hellfire sings -- in the Hindu Kush, not in pleasant Doha.