But isn't there supposed to be Eight Mannimarco?
There shouldn't be. The various Mantella outcomes do result in some contradictory events, like so:
Daggerfall awakens the Numidium, annexing the smaller kingdoms and crushing Wayrest and Sentinel. They assume power over the Iliac Bay.
Wayrest awakens the Numidium, annexing the smaller kingdoms and crushing Daggerfall and Sentinel. They assume power over the Iliac Bay.
Sentinel awakens the Numidium, annexing the smaller kingdoms and crushing Daggerfall and Wayrest. They assume power over the Iliac Bay.
As these three events happened simultaneously, the cancelled each other out. Think of it as rolling two balls into one another. They're going to collide, but not before having rolled partially. As a result each of these kingdoms partially conquered the Iliac Bay, and the fact that certain Mantella outcomes say that they triumphed over their adversaries is what omits them from being "integrated" into another kingdom.
I don't get how that necessarily applies to the King of Worms, though. There should only be two - mortal King of Worms (all Mantella outcomes sans his) and divine King of Worms (his Mantella outcome). The only way I'd understand there being eight is if the Dragon Break occured as if "okay, the Daggerfall/Wayrest/Sentinel/Gortwog/Blades/etc. endings all left the King of Worms mortal, so there's going to be 8 of them now." Not necessarily as he was not affected by those outcomes so he should not be affected whatsoever. Uriel Septim was not involved directly in any of these time warps, and you don't have eight of him running around (though it may explain the strange hair patterns and illegitimate sons). :ahhh: