Why didn't the USA first evacuate civilians then focus on evacuating their army from Afghanistan?

https://www.youtube.com/watch?v=wjF-8lZcTfQ

At 2:30 in this video Russel Berman points out that civilians should have been evacuated out first and then the military should have been evacuated. This seems like a fairly effective strategy lowering risk on US personnel.Also, as the Taliban was advancing towards Kabul (while the US was pulling army out) why didnt the US temporarily stop evacuation and focus for some time on the evacuation of personnel(particularly Afghans at risk from Taliban-controlled areas)?