He only wanted to leave because after that season everything was about how Messi pulled the team from the depths. In reality, that season you could argue that in the big matches Neymar was the real difference maker. And when you saw all of the branding around Barca it was Messi and no one else. That might have been cool for Suarez who was also 30, but Neymar never felt like Barca was going to be his team....that's the boards fault.
You look at Man City. Augero is arguably a top 3-5 striker in premier league history, Kompany held together a poo-butt back line, David Silva their key playmaker...and yet when KDB came around it became HIS team.
Messi understood, in the same way that Ronaldinho did for him, that Neymar was to inherit Barca. He didn't want to leave, and Messi/Suarez didn't want him gone either. But Neymar Sr. and his camp leveraged the board's ineptitude and lack of context. This IMO comes from not having enough "footballing" voices in the room. And Abidal was a terrible executive.
Barca's board felt like they would have Messi FOREVER. They are learning the hard way.