When plans for the Sea King Inheritance were being made by Sebastian, Old Mak, and their allies, they planned with the conscious knowledge that Sebastian was a highly wanted predator by the Atlantians.
Because of this, in the plan, they emphasized that once the battle began, in the chaos if the Atlantians tried to pick out Sebastian from the rest, they would hide in the dark and stealthily provide help.
In a chaotic battlefield like the one after the Toad Alliance and Turtle Confraternity's warships appeared, Sebastian's chances of surviving the onslaught of the Atlantians were pretty high.
Unfortunately, life was too unpredictable.
The appearance of the Annihilation Division Fleet spoiled everything. The appearance of this Division Fleet immediately placed the Atlantians above all.
The chaos that the predators caused was nullified instantly, they had the situation in control once again which was something that Sebastian dreaded to see.