Boxoffice poison

It's surprising that MGM made two movies dealing with the plight of American GIs in North Korean prison camps - "Prisoner of War" in 1954 and "The Rack" in 1856 - even though they must have known that such somber subject matter had little appeal at the boxoffice. What motivated them to do this? Today, alas, movie studios tend to avoid anything that might be labeled "serious."