I really can't disagree with that last part. I mean it doesn't matter as they would know whether it was the winter or summer season. They simply know what's going on in their villages to know if we were pulling out. They just knew us better than us sometimes, and that's a fact. Anyways as for the letting people know, it was broadcast to the world and too late. With that knowledge the Taliban simply waited until we were out of the villages to sweep in. I mean we fought hard (I know I lobbed a goodly amount of HE at the Taliban and bombs) just to keep it secure, but again all they had to do is wait until we pulled out to retake those same villages. So yeah, there's some blame all around but nobody thought the Taliban would sweep in. I mean I saw some footage from an OSINT account on Twitter so it was no surprise that they were chasing away the Afghan forces we setup but yeah, announcing it was stupid, but then again they would have figured it out anyways I think.
As for a waste of money if we had stayed, it would definitely have cost us more for what we got. We only didn't delay it by a motion of ten years or however amount we would have spent if we stayed. We had to leave sometime of course and frankly glad we did in some ways.