> Leaving Afghanistan (to fail) has been a long time coming. Obama wanted to do it, Trump wanted to do it, Biden decided to pull/had to pull/tripped over the cord.
I don't think blaming the failure on Obama, Trump, or Biden is fair. Even blaming the failure on the way Bush handled the invasion after it began is unfair, since I think it was doomed to fail from the very moment of conception. I don't think it ever stood a chance of working in the first place.
Anyway, if you'd like to know more, there are interesting parallels between the Taliban's resurgence in the past few days, and the rise of the Saqqawists during the Afghan Civil War in the 1920s. Amanullah Khan's government and armed forces were struggling against a rebellion of tribal forces (the Shinwari) who opposed Amanullah's attempts at reform, particularly wrt the status of women. When Amanullah's forces were preoccupied with fighting the Shinwari, the Saqqawists used that opportunity to attack Kabul, which Amanullah's forces surrendered to the Saqqawists with almost no fight (sound familiar?)