You are a fucking moron. The date was set by treaty. No, Biden could not just indefinitely postpone the withdrawal, given that Trump had already committed the US. As it was, Biden delayed the departure a little bit, but American presidents are actually supposed to follow treaties established by prior presidents. It's how our system is going to work.
The fault for the timing is on Trump alone. He was the one trying to score political points, which is why he acceded to such a shitty treaty. The Taliban ate Trump's lunch when negotiating the deal. Think about it. Trump gave up a lot of concessions to the Taliban. He could have just left without committing the US, but he didn't want to do the dirty work.