First, Talleyrand was for Talleyrand and for a France where he could live in luxury and generally take advantage of people as naïve as the Bourbons.
It is important to remember that Talleyrand was sacked by Napoleon for rapacity and was in the pay of Napoleon's enemies. Then before Napoleon he had been involved in the infamous XYZ Affair with the United States-again for profit trying to get bribes from American officials which they refused. He was a blackguard and that was that.
Second, Bernadotte and Marmont blackened their own reputations and it has been written about. They dishonored themselves as soldiers by not only in failing to do thteit duty, but the latter in betraying his own men to the enemy and breaking his oath of service. And he allowed Talleyrand to talk him into it.
Third, Dupont is indeed in a different category. His campaign in southern Spain is an example of exactly what not to do when faced with a popular insurgency. He allowed himself to be trapped and then made an agreement with the enemy while under their control which ultimately betrayed his own men to being prisoners under such deplorable conditions that only about ten percent survived. He deserved what he received when he and his immediate subordinates returned to France.
And being rewarded and employed by the Bourbons only made it worse.