Why? The ball gets bounced on the ground to a batter. Australian pitchers ("bowlers" in cricket-speak) have perfected their technique for drier Australian land that rewards fast bowling, but the English bowl slower and with a better swerve, which works well in soggy England. La Nina makes the Australian fields wetter like England, giving the English a boost. But in El Nino years, the Australian turf is drier, which favors the faster Australian pitchers.