Yea, the AIs must have different "Crack" criteria and thresholds. It might be set at the start of the game.
Some possibilities:
No CAP ship.
No CAP ship and no hope to build one within limits (time?). Can include no Cap Ship factory and lack of resources (including Credits). Note: If the AI can't scrap, then build space becomes a needed resource.
No Capital.
No Capital and No resources to designate capital within limits.
No Planet
No planet and No colonizer
No planet and No colonizer and No open planets.
Random BUG: Last AI standing will not Crack.