Firstly they never said that they would turn him to the US.

The Taliban government in Afghanistan offered to present Osama bin Laden for a trial long before the attacks of September 11, 2001, but the US government showed no interest, according to a senior aide to the Taliban leader, Mullah Omar.

Wakil Ahmad Muttawakil, Taliban’s last foreign minister, told Al Jazeera in an exclusive interview that his government had made several proposals to the United States to present the al-Qaeda leader, considered the mastermind of the 2001 attacks, for trial for his involvement in plots targeting US facilities during the 1990s.

…

Robert Grenier, the CIA station chief in Pakistan at the time of 9/11, confirmed that such proposals had been made to US officials.

Grenier said the US considered the offers to bring in Bin Laden to trial a “ploy”.

…

Subsequent to the 1998 US embassy bombings in Kenya and Tanzania, as US pressure grew, the Taliban insisted on a procedure under the supervision of OIC because it considered it a “neutral international organisation”.

The OIC is a Saudi Arabia-based organisation representing 56 Muslim nations. Al Jazeera contacted the OIC, but nobody was available for comment.

…

Muttawakil, who now lives in Kabul and advises an Islamic educational foundation, reportedly tried to negotiate a ceasefire in the days after the US launched operations in the country in 2001 by seeking to convince Mullah Omar, the Taliban leader, to part ways with bin Laden.

He was taken into US custody in the notorious Bagram prison early in 2002. After months of detention, he was released under house arrest in Kandahar and then moved to Kabul.

So hey, in fairness, maybe the guy we illegally tortured for years at Bagram may have stretched the truth. But it appears the US CIA station chief simply didn’t trust the Taliban in the run up to 9/11 and decided it wasn’t worth the trouble to negotiate.