As real as any reasons we are privy to, it seems like the obvious seed of contention. PATFO wanted to structure his contract like Duncan's, by backloading his salary while Leonard wanted it upfront. Aldridge's extension impacted on Leonard's desire. When neither side relented, PATFO started using Leonard's then-recent slew of injuries to lowball him and then Unc responded by leaking their request for a trade. Remember that clip of Leonard gingerly mounting the airplane stairs? Was that staged as well?
There's also this factor to the equation:
https://www.sandiegouniontribune.com...227-story.html
His girlfriend was pregnant with his daughter the season he went for second DPoY, all-star and all-nba in a 67-win squad. Then, the season he became a first-time father, he went for mvp, finishing second in voting. He was checking all the requisite boxes for a supermax contract. This was also the season when Aldridge's request for a trade was made public. The season after that was the season leading into Leonard's supermax eligibility. So yeah, his goal seemed obvious to me and not getting it was a dealbreaker. And I think San Antone media knows it too but since Leonard never raised a public stink about the supermax, they followed suit and pursued other narratives, consequently saving the franchise some face.