This is the only conclusion I could reach also. I don’t think incompetence could possibly be to blame for this happening. If this wasn’t the plan, then some people need to go to jail for treason. This has to be the largest amount of military equipment in history that one entity has given to their enemy.
That's a lot of equipment to leave behind for the Taliban to have, while US allies will likely have to beg for the procurement of this equipment. It's the money of the people paid by the taxes, the impression is that they really scramble to fly away.
Using the Taliban against China, Russia, and Iran is possible but there were peaceful talks with Talibans and China already. There is no reason for Talibans to hate China, they have not done wrong to these people since and Russia is too far to barge again to make conflicts.