I think he did believe in the sanctity of marriage, and he probably felt that such a gesture was the last affectionate thing he could do for Eva Braun at that point to, as Charley said, honor her fidelity.

What's so hard to understand about it? Those people didn't think of themselves as evil, they thought they were the "good guys", losing out to the "demonic" Communist hordes who would swallow all of Europe if they failed.

Ebbie, I suggest you watch the entire movie "Der Untergang" on Youtube (if you haven't already), and consider all the various thoughts that might have been going through their minds. Remember, they thought they were the good guys, the tragic heroes going down fighting, the defenders of western civilization. If they had won the war and become the dominant power in the world, that's exactly what future generations would have been told about them, I'm sure, and you wouldn't be hearing about death camps at all, unless they were the Stalinist death camps.