User blog comment:Thedoucheinthenorth/The Civil War - Why it is great/@comment-71.215.4.247-20121208173049/@comment-3492791-20121208180722

The implication is that Ulfric didn't want to risk the moot choosing someone else, so went to war and he replaced all the jarls that opposed him to ensure he did.

Being a dragonborn does not make you the Emperor, being of the royal family does. The royal family is the Mede line now.

The Amulet of Kings was also destroyed by Martin Septim.

The Dominion is not going to care who the emperor is. The only difference is they might get to go to war faster depending on who's in charge.