The worst Axis errors belonged to governments, not uniquely foolish navies

Which World War II navy was the most foolish?

No single navy; the more serious folly was in German and Japanese governments knowingly accepting disastrous strategic odds.

Most navies understood many of their own limitations. The deeper failure sat with German and Japanese governments that recognized structural strategic problems and proceeded anyway. Naval procurement could reduce particular weaknesses but could not supply the missing resources, industrial balance, or favorable geography. The more serious error was the civil-military decision to enter an unwinnable strategic contest.