The short answer is because they were ordered to do so. For all the stupidity behind the Biden’s policy. This has been significant technical achievement. No other country has the capability to do something like this.
This has been a pretty well done, up until they get the aid off the pier. Then the fundamental weakness and false assumptions Mr. Biden and his team run smack dab into physical and geopolitical reality. This was stupid idea, and the fact that it was well executed doesn’t make it any less stupid.
Our military is a jobs program at this point.