Well, if they're still not married, he's still just a General.
Politics, even if he's a Messiah, he's still not a King.
Gotta love it.
As far as he's come Griffith is still just a general, he still has to play it by the book, even if he marries Charlotte, he will only be a prince.
I don't think you understand the point of my comment. There is no way in which Griffith is "just a general". He's pretty clearly the one making the rules in Falconia, a city created in his image and in which he regularly performs miracles.
The rationale that he needs to marry Charlotte and get the Pontiff's approval before he can access the throne is paper thin. It always was, but the more time passes, the more obvious it must be even to the average citizen. So I'm curious to see what will actually justify it in the story.