It would seem that Joe is not wrong insisting that he was simply executing the agreement settled by Trump: an agreement that we can now infer included Taliban control of Afghanistan as well as diplomatic recognition (that's coming).
Obviously, the powers-that-be thought this was a good idea regardless of the person sitting in the Oval Office. The real question is why? Why surrender a key piece of real estate within striking distance of Iran and China (and of interest to Russia for pipelines)?