The Afghan military significantly relied on (mostly) American airpower to keep the Taliban at bay. The Afghans generally fought well knowing that American jets and helicopters were available to take out Taliban targets. (Edit to add that I will concede that outside of a small group of special forces that generally fought well, much of the Afghan army was pretty inferior to the Taliban without air support).
Biden’s sudden decision to withdraw left the Afghanis with their ass out hanging in the breeze. Not only did they did suddenly lose American air support, they lost on the ground expertise in keeping the Afghan Air Force flying. I read that the Afghans were having to resort to Zoom calls with contractors for guidance on repairs.
Biden can try to blame Trump and / or the Afghans all he wants, but he owns this failure and its consequences….completely.