Odds are based on how people bet not who vegas actually thinks is going to win. When the set the original lines, they are going to give bigger payouts for teams they feel are longshots to encourage betting. Once people start betting, odds will fluctuate depending on how many bets they are collecting. It is set up so it doesn't matter who wins, Vegas will still always collect more than they'll pay out on winning tickets. The odds have no basis in reality other than to serve as an enticement to get people to bet on all possibilities. Vegas doesn't care who wins because they ALWAYS win.. well almost always.