Trump's schedule was for exit by May – or about 100 days after the inauguration of President Biden.
Any responsible/competent administration would have been well into the planning - if not implementation - of extracting our allies. Didn’t the DoD believe Trump meant what he said/
I suspect that, as with vaccine administration, Biden's administration was not briefed in advance, and, after inauguration, discovered that substantive planning had not been done.
Why hasn't the media pursued this? It's an obvious question, but mainstream media seems to be more interested in playing blame and gotcha with the Biden administration, which inherited the problem, rather than asking legitimate questions about the Trump administration, which created the timing and terms of withdrawal.