User blog comment:Tommy,Klaus&Kol2012+/One character that probably wont return(spoilers ahead)/@comment-74.132.82.188-20190707210246/@comment-74.132.82.188-20190708193056

We will have to agree to disagree. I don't think Mark owes the fans anything.

So there are certainly more knowledgeable people than I on this topic, but Mark felt that Crowley's arc was done & he thought the writers had no new ideas for the character. TPTB chose not to continue his contract. Crowley's death wasn't a surprise to him. He had some input into his final scene, the scene was filmed that way and then edited differently. There are many articles on this topic. Here's one link: https://www.syfy.com/syfywire/mark-sheppard-supernatural-nycc-2018-panel When he initially left the show, he was more discreet in his answers, but he is more clear about what happened as time has passed. I have never heard a response from TPTB, so I don't know their version of the story. But Mark has been consistent from the end of S12 that he wouldn't be back.