Trump was depending on the US military generals to train and motivate the Afghan army. They failed miserably and the head of the Joint Chief’s of Staff should be fired, today..
Trump and Pompeo dealt with the Taliban, successfully. During the last 18 months of his presidency Taliban didn’t make a move against the US. If they had, he would have ordered one or more of the Taliban leaders killed. And they knew it.
If Trump were president today, this would not be happening. If Taliban violated any of the agreements made with the Trump team, they knew there would be fatal consequences. He had already established his MO - kill the leaders and the rest fall in line.
The Taliban didn’t make a move while Trump was POTUS because they knew we were leaving. They didn’t want to give the endless war lobby a gift, obviously.