Just had a thought since the Japanese had not developed a means to sustain carrier operations at sea, would that be one reason Yamamoto had relied on his BB's so much. It wasn't until 1944 that the US had fully developed the logistic support that enabled their carrier groups to stay at sea. I wonder if Yamamoto had reasoned that the US carriers would be good for one battle so even if they had hit some Japanese carriers they probably wouldn't be able to stay for a second,this assumes that not all four would be sunk. Look at how effective the Hiryu was alone, imagine if two or three had survived. Once the American carriers would have to withdraw then BB's would be king.