I always thought he left New Orleans because he was "burnt out" but that was utter bullshirt, too. He didnt have his future HOF QB in Drew Brees' anymore and if he'd managed the draft proceedings better in 2017 and drafted Mahomes like he's said he was dead set on, he still be sitting in his office on Airline Dr. in Metarie. If Mahomes has 25-30% of the same overall career success in New Orleans that's he had in Kansas City, Payton is still proudly here, private resentments and all. His apologists and defenders can scream and go through all sorts of mental gymnastics or cherry-picked arguments with convenient twists applied here and there to explain otherwise.
I think most of Payton's insistences or drawn-out explanations surrounding why he didnt draft Mahomes, post-facto is carefully-crafted wish fulfillment. Payton probably wanted him at the time but he just couldn't bring himself to press the button because while Mahomes had an excellent collegiate career in a pass-heavy offense at Texas Tech, their was no guarantee that he would become 15% of the player he turned into. Not enough to convince him he was a worthy successor to Brees. Sure, he had a great supporting cast his first 4-5 seasons in Kansas City but even if he's not throwing for 5,000 yards and 40 TD's anymore, he's still making huge plays when needed to even if the Chiefs defense have become more pre-dominant. Mahomes' propensity for making great plays happen continually isn't a systemic thing, it's God-given talent which is why I suspect he probably wouldve succeeded where ever he went. That sort of immense talent or near-superhuman ability can't be taught.