Italian cruisers assigned to protect merchant traffic would have to remain near slow ships and interpose themselves against French attackers such as the Duquesne class. That defensive obligation removes the freedom to use speed for escape or wide maneuver. The attacker can break off, but the escort must remain in place and may have to accept the first hits. Italy therefore needed enough armored cruisers to hold position and absorb punishment while protecting the convoy, rather than a one-for-one speed contest.
Notable Point · 56:02-1:00:13
Convoy defense neutralizes a cruiser's speed advantage
An escort cannot run from a faster threat without abandoning its convoy, so protection and numbers matter more than headline speed.