The expected probability would have been for them to win 1.65 WS (13 * 1/8, the # of teams competing each year), so winning "only" 1 isn't quite as much of an underperform as is normally viewed. 2 would have been slightly exceeding expectations.
How did the Yankees win four in a row, five out of six years, and come within two outs in 2001 of making it five in a row? (Aside from having a balanced team that all hit well and fielded under pressure. And a manager who shielded the players from Von Steingrabber, most always.)