The current state of fan speculation, scored on two axes: how likely the theory is to land and how thoroughly it would break the internet if it did.
Kang exited stage left. The multiverse still has a bill to pay. Doomsday is the story of two universes colliding and Doom is the only person with a plan that doesn’t end with both of them gone.
The Kang dynasty stopped. The throne did not. Doomsday reads as a straight swap: every beat originally graphed for the Council of Kangs re-cast for a single antagonist with better production insurance.
Secret Wars is the sequel. Doomsday is the setup. If the structural role of this film is to put the multiverse in Doom’s fist, then he has to end the movie holding it.
The simplest read on RDJ’s casting is the scariest: Doom isn’t a coincidence, he’s a divergence. Somewhere on the Sacred Timeline, Tony Stark never made the Snap — and the man who survived became this.
The MCU has had fragmentary mutants for years. What it has not had is a Day Zero. The theory: Doomsday’s third act is the event that turns Kamala’s bracelet from anomaly into archetype.
Only temporarily. Only for math reasons. But there is an act two beat where the smartest man in any room looks at the smartest man in the next room and agrees, on first principles, that the Avengers are wrong.
Secret Invasion left Gravik dead and the Skrull population on Earth. Nick Fury is not in the cast list. One of the faces on the poster is the wrong one. We just don’t know which.
The one X-Men cast member who reads as a scientist first and a mutant second is also the one Doom can talk to as a peer. If there is a mole in the allied roster, it is McCoy.