Why were so many treaty cruisers badly matched to their navies?

Why did countries such as Italy, Germany, Japan, and Spain produce so many unsatisfactory cruisers?

Treaty limits forced different navies into a common cruiser category that often could not match their missions, leaving Italy with large, lightly protected ships that were neither expendable nor able to trade blows.

Italy needed either armored fleet units able to take punishment or numerous fast craft cheap enough to risk, but treaty categories pushed it toward intermediate cruisers. Cape Bon was tactically unfavorable: the cruisers carried fuel on deck, and radar-assisted destroyers approached from the coastward side thought safe. Even with those caveats, two cruiser-sized ships destroyed by destroyers illustrate the cost of combining large crews and targets with protection closer to flotilla craft. Speed was not armor once surprise and freedom to maneuver disappeared.