The contract between Sony and Amazon was for three seasons, so they had to do at least that many, breaking a contract is more messy than having to re-negotiate one. Plus, "Jordan Studios" was ended post season three, so having to not only do new contracts for actors, production team etc, they had to get new a new site for the in-studio parts. Too bad they didn't get a contract for five seasons, as ROP was able to, I think Rafe and co. could have come closer to semi satisfying ending with two more seasons.