A decent summary of the situation in Afghanistan seems to be the one in The Economist, which notes:
The Taliban, thought to number no more than 200,000 soldiers, armed mostly with equipment they have seized from their enemies, have taken all of Afghanistan’s urban centres in little more than a week, generally without much resistance (see map). The answer seems to be that what they lacked in brawn, they made up for in brains, determination and political shrewdness. For the past year, diplomats in Doha had hoped that the Taliban could be compelled to negotiate with Mr Ghani’s government to agree to some sort of power-sharing agreement. The insurgents evidently realised it would be more profitable to negotiate with Mr Ghani’s underlings, city-by-city, and thereby simply pull the rug out from underneath him.
Hence in Herat, a jewel of a city near the Iranian border, Ismail Khan, the warlord who took the city back from the Taliban in 2001, after fighting for days, surrendered and was filmed, in captivity, pleading for “a peaceful environment”. In Kandahar, the city at the heart of Afghanistan’s southern breadbasket and the birthplace of the original Taliban, the governor was pictured handing over to his Taliban counterpart. In Jalalabad, in the east, the Taliban marched in without firing a shot, after elders in the city negotiated a surrender. Mazar-i-Sharif, a northern city which once served as a bastion of anti-Taliban resistance in the 1990s, folded in similar fashion.
In each case, the militants have made wide-ranging promises, to “forgive” those who served in the American-backed government, in exchange for surrender. In Kandahar, former soldiers who surrendered have been issued with laisser passer documents that they can show at Taliban checkpoints. There, throughout Friday night the sound of gunfire echoed throughout the city. According to residents, it was mostly fired in the air in celebration.
The Afghan army, for all its apparent strength, seems to have fallen to what might be called Yossarian syndrome, after a character in Joseph Heller’s second-world-war novel, “Catch 22”. Yossarian was asked what would happen if everyone thought as he did that fighting was pointless, and replied he would “be a damned fool to feel any other way, wouldn't I?” Similarly, the Washington Post quoted one Afghan officer explaining why his soldiers would not stop the Taliban: “Brother, if no one else fights, why should I?” Afghan military morale was not helped by the government's fiscal crisis, which has led to government staff and troops missing pay for months.
What does the Taliban takeover mean? For all their promises to show mercy in victory, few among Afghanistan’s intellectual elite are reassured. After the militants took Spin Boldak, a town on the Pakistani border that was among the first to fall in late July, credible reports emerged quickly afterwards of dozens of government supporters being massacred. In Kandahar in late July, when the militants began to take the outskirts of the city, they kidnapped Nazar Mohammad, a popular comedian, and murdered him. Reports from Kandahar say that armed Taliban have been going door to door seeking out people who worked for Western governments. In recent weeks, thousands of refugees have collected in Kabul’s parks. Hundreds have mobbed visa-processing centres, hoping for a space in the last-minute evacuations being organised by Western powers.
The Taliban’s political arm in Doha has claimed that they are no longer the bloody theocrats who ruled Afghanistan from 1996 to 2001, when accused criminals were publicly executed at Kabul’s football grounds, including women who were stoned to death for adultery....
The big geopolitical question arising from this is what China will do. It's hardly going to be seen as a friend of Islam, given their massive attempt to end its influence in its own territory; but on the other hand, minerals and money. US News wrote:
At stake for Beijing are agreements it has already secured from the Taliban not to harbor inside Afghanistan any Islamic extremists with designs to wage insurgencies in parts of western China, notably the restive Xinjiang province – a promise that far exceeds anything the U.S. has been able to extract with regard to the persistent threats of al-Qaida operatives partnered with the Taliban.
Any sort of stability in Afghanistan would also allow China to reap the benefits of prior economic investments in the region, including mineral rights in Afghanistan. Buried in the latest report from the U.S. inspector general overseeing reconstruction in Afghanistan was a little-noticed observation that China has dramatically increased its economic interests in Afghanistan recently, encouraging the completion of a road in the Wakhan Corridor – the sliver of land connecting the two countries. It cited an Afghan Public Works Ministry spokesperson who said, "China has expressed a huge interest for investment in Afghanistan, particularly in the mining sector, and this road will be good for that, too." The Taliban recently seized wide swaths of that territory as part of an apparent campaign to control Afghanistan's northern border crossings.
China also seeks stability in Afghanistan for the sake of regional infrastructure projects it's already pursuing in neighboring Pakistan as a part of similar investments globally known as the Belt and Road Initiative.
I get the impression it will all end in tears.
Finally - I will repeat the observation I have made before: I don't understand how, in modern times, Islamic fundamentalist inspired leadership which is willing to rule on the basis of terrorising its own population retains any popularity at all. I don't understand these societies.