Hasn't that been the problem all along? People we were "training" one day would turn on us the next day. They only pretended to be loyal to whoever was paying them & you could never tell who was your ally or or enemy.
That's why, to me anyway, it is now surprise the people we trained were not loyal to us & would never be able to hold the country. The Taliban retaking the country was inevitable, either 10 years ago, or 20 years from now. Yes, it could have been a whole lot more orderly, but it was going to happen whenever we left.
Same happened in Vietnam.