"[I]t seems that the president simply didn’t want to appear to be abiding by the terms of a deal negotiated by his predecessor."

Mike Pence writes in "Biden Broke Our Deal With the Taliban/It’s a foreign-policy humiliation unlike anything our country has endured since the Iran hostage crisis" (Wall Street Journal).

In February 2020, the Trump administration reached an agreement that required the Taliban to end all attacks on U.S. military personnel, to refuse terrorists safe harbor, and to negotiate with Afghan leaders on creating a new government." 

As long as these conditions were met, the U.S. would conduct a gradual and orderly withdrawal of military forces. Unanimously endorsed by the United Nations Security Council, the agreement immediately brought to Afghanistan a stability unseen in decades. 

In the past 18 months, the U.S. has not suffered a single combat casualty there. By the time we left office, the Afghan government and the Taliban each controlled their respective territories, neither was mounting major offensives, and America had only 2,500 U.S. troops in the country—the smallest military presence since the war began in 2001. 

America’s endless war was coming to a dignified end, and Bagram Air Base ensured we could conduct counterterrorism missions through the war’s conclusion. The progress our administration made toward ending the war was possible because Taliban leaders understood that the consequences of violating the deal would be swift and severe. 

After our military took out Iranian terrorist Qasem Soleimani, and U.S. Special Forces killed the leader of ISIS, the Taliban had no doubt we would keep our promise.  

But when Mr. Biden became president, he quickly announced that U.S. forces would remain in Afghanistan for an additional four months without a clear reason for doing so.  

There was no plan to transport the billions of dollars worth of American equipment recently captured by the Taliban, or evacuate the thousands of Americans now scrambling to escape Kabul, or facilitate the regional resettlement of the thousands of Afghan refugees who will now be seeking asylum in the U.S. with little or no vetting. 

Rather, it seems that the president simply didn’t want to appear to be abiding by the terms of a deal negotiated by his predecessor. 

Once Mr. Biden broke the deal, the Taliban launched a major offensive against the Afghan government and seized Kabul. They knew there was no credible threat of force under this president....

Did Trump have it set up for orderly withdrawal? Perhaps Biden can't say why he didn't execute the Trump plan, but if he doesn't provide a reason, many of us will assume that he simply did not want to acknowledge that Trump had done something right. The burden of being in office is that we get to see how your approach worked, while your erstwhile electoral opponent can talk about what might have been. 

Your defeated opponent could refrain from talking about it. He could keep quiet and let the President retain whatever respect is left. To paraphrase Pence: It seems that the former President simply doesn't want to appear to be acceding to the approach to withdrawal adopted by his successor.

I'm quoting Pence's WSJ piece, but Trump is also speaking: "Trump releases 12 statements in five days attacking Biden while whitewashing his own role in Afghanistan withdrawal/Most agree there’s plenty of blame to go around for US mistakes in Afghanistan. Not Donald Trump" (The Independent).