[table] Stat | Last Year | This Year
GB% | 34.4% | 48.3%
HR/FB% | 13.0% | 8.9%
HR/G | 1.41 | 0.66[/table]
More ground balls means fewer fly balls; fewer fly balls, plus fewer home runs per fly ball, means fewer home runs. Fewer home runs means WAY fewer runs.
That, plus the reduction in BB you cite above, accounts for the difference.