Scheduling. I think it’s also important to remember that things like, filming in toronto in mid winter and just how vile of a character Mason is, stuff like that is gunna be grating on a person. Mason isn’t a regular and for that reason Michael might view Mason as actually, not that important. They’ve moved several of the female characters (Bedelia and I think Freddie?) up to regular to stem the (probably unavoidable) sausage fest there, no space for more sausages unfortunately. Mason was always going to be a guest and now he’s a guest who is almost entirely paralysed, the actor has to spend half a day in makeup per shoot or something mad. I can see why Michael maybe thought, if he was gunna go, now would be the time. Mason is essentially a tricky character to deal with, all of this may have aided his decision.
It was Michael’s decision and I wouldn’t want them to make him stay against his will, in this sense I don’t know why some people are upset/angry, is that what they’d rather? I’m sure they tried everything to jiggle things round but with the nature of it they don’t have a lot of room to jiggle.
Shit happens. Essentially. Peoples time and lives don’t fit together perfectly. People like Mads, Hugh, Caroline, Laurence and Gillian all have a huge block of time to dedicate to it, which is in some sense easier. It’s like Tucker, though I’ve seen some more stuff about a confirmation on having Matt in season 3 (?) Kingdom is now a huge show with a ton of acclaim itself, finding a few weeks might be difficult for him too, I hoping Matt is involved but I’m surprised Tucker will be able to find the time. You know?
So yeah, he backed out, the easiest reason to give in that scenario is “I’m busy with other shit” but I can think of other factors. The role of Mason doesn’t seem appealing in the slightest, particularly not now. (Remember Pitt got the role after people turned it down, he stepped up to the plate when others wouldn’t have, they read the script and said no.)
So yeah, kinda what I’m saying is, official word is scheduling problems but I’m inclined to believe it was that plus other factors. Hope that helps.