What needs to be taken into account and included in the discussion is the evolutionary path of increasingly larger steam plants and diesel engines. I sailed on WW2 built ships and they were 450 psi sectional header boilers. From there I moved onto 600 psi and finally 1000 psi boilers. Steam plants moved up the developmental path quicker than their diesel counterparts.The largest single diesel engine built up until the early 1960’s was a B&W engine of 22,000 hp. The footprint of that engine today would have 3 to 4 times the horsepower. It took some time for the diesels to catch up, but catch up they did if you look at what is being produced today.