Destroying the abbey didn't help the allied cause. The Germans hadn't occupied it but afterwards used the rubble for good defensive positions.
I’ve seen that fact in a number of presentations on the Military channel. the rubble was a better high ground than the abbey itself. but who knew. all the allies knew was that the Germans had it and we needed to take it....
the allies did amphibious end runs around German lines on the peninsula though...like Anzio....but I do believe the mountainous spine of Italy was not completely defeated till operation overlord when the focus was on northern france and the Germans sent troops up that way...as did the allies.
By the way, he really did torpedo a ship that he mistook for the Ranger.
The Germans learned that lesson from Stalingrad, when the Russians used the rubble there to their advantage.