...Which, at the time, wasn't the thinking, given that the naval brass still thought battleships were the big thing (and for some things, they were).

FDR, and others (e.g., Churchill), thought the Japanese had rational leadership which could be deterred.  FDR and his advisors also feared being dragged into an Asian war, when they wanted to intervene in Europe -- until Hitler quite unpredictably joined these two conflicts, there was no "the war" in existence.

Beware of backcasting, based on what we know now.