If you fail to plan you plan to fail. That is what went wrong for the United States in Afghanistan. 1) No clear goals, no end of mission. Nation-building is not a military objective. 2) When leaving, no plan for an orderly withdrawal. The troops pulled out in the middle of the night stranding thousands of American citizens, Afghan allies and the Afghan National Government. 3) No support for the people who would have continued the fight without us. Trump's plan was a phased withdrawal using air assets to support the Afghan National Army. Buy-den had not plan except "Go home." 4) Lack of leadership at the highest echelons of the military. Mark Milley is an oath-breaking fool who couldn't plan an orderly withdrawal from an Uber car. The emphasis is on "Diversity and Inclusion" to the detriment of all else. This is reflected in the choices made for leadership positions all the way to the Central Command.
It only took seven months for Joe to live down to Obama's expectations.