Why did the visa arrangements and military equipment recovery not happen before US and allies leaving of Afghanistan?

As the US and allies are leaving Afghanistan they seem to leave behind quite a lot of military equipment and a lot of persons who struggle to leave Kabul.

I am wondering why this is happening since leaving Afghanistan became clear as early as in April 2021. There were several months sufficient to establish a visa mechanism for NATO collaborators, journalists, and their families (who are in danger now), so they are able to leave Kabul before the Taliban reach it.

Why this apparent lack of preparations for the civilians surrounding NATO presence in Afghanistan?