The worst thing that could happen to the Taliban is for them to win. Their last go at running the country was an unmitigated disaster. There is reason the 2001 air campaign defeated them in 20 days. They had squandered almost all of their popular support.
The Taliban is ultimately just another outsider supported invading force. They will get their arses kicked like everyone else who tried to upset the natural conglomeration of decentralized provincial ruler model, that has existed in Afghanistan for hundreds of years; in favour of a centralized autonomous governing power.
Plus the vast majority of the Taliban are good at killing people and blowing things up but have none of the actual skills required to run a country. The abject failure of ISIS to hold on to their conquered land is a useful recent example of the strengths and the weaknesses of these kinds of movements.