The Wrap claims that it all boils down to Ryan Reynolds' renegotiated contract, which fetched the actor a hefty pay raise. He also got casting approval and several other creative controls. The movie is said to be without a release date at this time solely because of this.
The whole contract renegotiation is said to have taken longer than Tim Miller was comfortable with. And it suddenly shined a light on some hefty differences between the two parties. Miller, who owns his own VFX studio and did a Deadpool effects polish, was lobbying for a much more stylized sequel. Reynolds, on the other hand, was seriously pushing the raunchy comedy that landed the first movie its R rating.
But it was the casting of Cable that proved to be the last straw. Kyle Chandler of Friday Night Lights fame has long been rumored for the role. And Miller was lobbying for the Bloodline actor to win the part. Rayn Reynolds didn't want Chandler in the role, and the studio decided to back its leading man. Chandler is much younger than Cable is actually portrayed in the comics, and it's possible that Reynolds wanted to stick to that by casting an older actor.
