The campaign fleet has become so large that rival powers no longer respond to deliberate provocations. That amounts to deterrence inside the simulation, even though the player wants a war. Prestige comes from letting an opponent declare war and then defeating it, so the game rewards a conflict the fleet is already strong enough to deter. The proposed response is to cut ships until another power is willing to fight, a campaign incentive rather than advice for a real state.
Notable Point · 2:18:54-2:19:17
Fleet deterrence versus campaign prestige
The oversized campaign fleet deters rivals, while the prestige system gives the player a reason to provoke a war instead.