I voted for Biden in 2020. It feels better to say this wasn't his fault for those of us who voted for him. It was his fault, and primarily a failure of his administration, especially Jake Sullivan, who is the least qualified National Security Advisor I've ever seen, including those who advised GW Bush, which is saying something. His qualifications are primarily political and partisan, and he's incredibly thin on actual defense matters. Feel free to take a look at his background, and prepare to be depressed that he wasn't fired immediately after that fiasco. In fact, nobody was fired from the administration, which for me was the most horrifying part. Obama's administration NEVER WOULD HAVE LET THIS HAPPEN.
Specifically, "the planning by the military" was under constraints placed on it by the executive branch. (The constraints were that no more troops would be added on the ground to "cover the withdrawal" and that all civilian contractors had to be out of country months prior, which immediately destroyed all air capability depended upon by Afghan forces) And the idea that Biden was committed to any plan concocted in the Trump administration is absurd. (this treaty was already long in violation by Taliban as well) Nobody who voted for Biden, myself included, expected (or wanted!) him to cling to any plans developed by the previous administration. It's an excuse. I'm a former defense/intel contractor, I've been to Bagram on multiple occasions, and everyone in the DoD community knows that this was an executive branch mistake conflated with malignant obedience at the Pentagon command level.
In case I sound partisan (I'm not), let me be extremely clear in my statement:
The botched withdrawal of Afghanistan NEVER WOULD HAVE HAPPENED under Obama. His administration was vastly more competent than the current one, on multiple matters.
Without a surge of troops to cover withdrawal, the US embassy in Kabul could not be secured simultaneously with Bagram. The decision was made to instead focus on securing the embassy AND HKI airport and to abandon Bagram instead. As is typical of decisions coming from the top levels of the Pentagon under intense executive pressure, all feedback from the ground of the plan's lack of feasibility was ignored, along with warnings of the rapidity of ADF collapse once civilian contractors were pulled from the hangars.
I'm stating this because, not unlike the highly partisan administration under GW Bush, when partisans get too much power in administrations, you get disasters like this. Partisans are selected for loyalty over competence, and it's a growing epidemic in US politics that partisans get more and more power in successive administrations.