It’s unusual for a president to pardon someone who pleaded guilty before they are sentenced, but pardoning General Michael Flynn on Tuesday may be the least bizarre and destructive thing Trump did in relation to this investigation.

Flynn resigned in 2017 just 24 days after he was named Trump’s first national security adviser, and four days after public reports that he discussed U.S. sanctions with the Russian ambassador despite repeated denials from the Trump administration that he had done so. Months later, Trump tweeted that he “fired” Flynn because he “lied to the Vice President and the FBI.”

Yet a day after Flynn resigned, Trump met with FBI Director James Comey and several other officials in the Oval Office. Trump excused all of them from the meeting except for Comey, stating repeatedly that he wanted to speak to Comey alone. When the others left, Trump told Comey that Flynn was “a good guy” and urged him to “see your way clear to letting this go, to letting Flynn go.” Comey did not do so, and less than three months later, Trump fired him.

Comey’s firing ultimately resulted in the appointment of Robert Mueller as special counsel, leading to a multi-year criminal investigation that Trump publicly and privately obstructed. While Mueller famously refused to reach a conclusion regarding Trump’s criminal liability, I was one of over a thousand former federal prosecutors who concluded that Trump obstructed justice. If Trump had pardoned Flynn instead of secretly pushing Comey to drop the investigation, none of that may have happened.

Mueller took over the investigation of Flynn, who pleaded guilty to lying to the FBI as part of a cooperation deal with the Special Counsel’s Office. At the time, that looked like a favorable agreement for Flynn, who may have faced additional charges and was looking at a likely sentence of probation or minimal prison time.

The Justice Department successfully argued that Flynn’s guilty plea should stand, and because Flynn had failed to fully cooperate with the Justice Department after Mueller’s investigation ended, the DOJ later sought a prison sentence for Flynn. But in January, the Justice Department abruptly changed course, suggesting that probation would be warranted even though Flynn was not fully cooperative.

The Trump administration then sought to dismiss its own case against Flynn, an extremely unusual move given that Flynn had already pleaded guilty. DOJ argued that “newly discovered evidence” revealed that Flynn's lies to the FBI were not “material” to the FBI's underlying investigation. The “materiality” requirement is just that the lie was “capable of influencing” the FBI, not that it actually did.

Needless to say, that is a standard that is very favorable to the Justice Department, which routinely argues that it should apply despite widespread criticism from defense attorneys. Not only did the DOJ contradict its own longstanding policy, but it did so due to the notes taken by the FBI of their interview with Flynn, which DOJ was aware of all along.

The judge in that case found that this stunning reversal by the Justice Department smelled so fishy that he appointed a retired judge who had publicly criticized DOJ’s about-face to argue against the dismissal, given that both sides in Flynn’s case supported it. When Flynn appealed the judge’s decision to appoint the former judge to argue the other side of the issue, Flynn appealed, and Trump’s Justice Department sided with Flynn.

Flynn’s appeal ultimately failed, and the case is still ongoing, but the Justice Department diminished its reputation, contributed to growing concern that it had become politicized, and created a precedent that will haunt it for years to come. But the harm to the Department of Justice would have been avoided if Trump hadn’t postponed this decision until his electoral defeat, implicitly acknowledged by the pardon, forced his hand.

Many have decried Trump’s pardon of an unrepentant liar whom he obstructed justice to shield, but the real damage was done by the president over the past four years. If Trump had pardoned Flynn in the beginning, he would have saved himself a lot of headaches and the Department of Justice wouldn’t have embarrassed itself by giving special treatment to the president’s friend. Like many of Trump’s decisions as president, how he reached the decision was worse than the decision itself.