I was watching my DD's college softball game. It was 2-2 bottom of the 7th with a runner on 3rd 1 out. We were in the field. A pop fly in foul territory by 1st. The first baseman makes a diving catch. The batter was running up the 1st base line and stops and turns to go back to the dugout at the same time the runner on 3rd tags up and heads home. The 1st baseman throws to home but hits the batter, who was still walking back to the dugout. The ump ruled interference by the batter so we ended up with a double play to end the inning. We went on to win 4-2 in 9 innings. I was happy with the call but thought it should have gone the other way. Can anyone explain why it didn't?