TL;DR: The war was stupid from beginning, it should not have happened and it accomplished nothing. There was a power vacancy after US withdrawal and Taliban filled it. The military industrial complex did it's thing

Osama bin Laden/Al Qaeda did 9/11

Bush started the war on terrorism and refused when Talibans offered to extradite bin Laden multiple times.

USA invaded Afghanistan and the on ground troops were begging for reinforcements to seal the border but Bush and dick rejected the request.

Bin Laden would later slip into pakistan and USA stopped pursuing him even though pakistan complied and infact, the CIA section chief of Islamabad, Robert Grenier had already made full arrangements with Pakistan army and frontier corps to help the pursuit of bin Laden if he had crossed the border

USA would later set up a democratic government in Kabul in which, women were granted right to and more freedoms.

Obama drastically expanded the US presence in Afghan, from 30,000 to more than 100,000 troops at the peak. While Trump escalated airstrikes, he successfully signed a deal with Taliban in Feb 2020. Although Biden said the deal is cancelled 2 weeks into his presidency, he successfully withdraw.

The US was always going to leave sooner or later, and the Taliban were always to be in a good position for the final offensive war when it did. It's inevitable.