I am no expert on the situation in Afghanistan but, as far as I know, the terrible poverty is mainly due to two factors. One is the dependency upon international aid, which used to make up 45% of the gross national product. As soon as the Taliban took control, all this aid was immediately cut off.
The other reason is the freezing of Afghan assets. The banking system, including the Afghanistan Central Bank, has ground to a halt. Though this is meant to act as sanctions against the Taliban, it inevitably hits ordinary people because they can't access their money, if they have got any, and charities can't move funds into the country. According to the New York Times, Afghan accounts aren't just frozen for political reasons (eg by the US government) but also because foreign banks think that they are just too much hassle.
Some charities are trying to buy food in other countries and bring it over the border, as they can't access money in Afghanistan because the banks are closed, but obviously that cannot be easy either as you would have to deal with Taliban border guards.