I’m leaning towards it being an actual personal issue.
You don’t fire your DC one week before your first game over a football disagreement, you work it out and move on. Plus Mora is the HC, he can just demand something be done his way. The football reasoning would be understandable if it happened weeks ago, there’s no way Mora just figured out they aren’t meshing well enough.
Plus we know Spanos has dealt with a lot in his life recently, might not be able to handle the added stress of travel and game performance at the moment. I don’t think it’s so crazy that a rich man with many personal issues might make a decision to alleviate a heavy burden like this.