Doom is time-slipping and dream-walking into his own variants.
Re-posting my post from /MCUTheories:
That scene in the trailer in which Doom flies out of the window and does some freaky shit in the air before landing. This snapshot of it reminds me of Loki time slipping and then it occurred to me he could also be dream walking like Strange and Wanda did. He's intentionally exacerbating the incursions and accelerating the destruction.
We know there's at least a couple Doom costumes that we've seen in the trailers/F4. Whether it's one Doom doing wardrobe changes or different Dooms is unclear.
Then there's a couple more scenes in the trailer that look different with this theory in mind.
Sue Storm: "...he used to be different." - He could be changed by the events ("everything he loved was taken from him") AND he could literally be changed by a variant Doom taking over him.
Reed Richards: "Victor, did you do this?" and he looks at him with a pensive blank stare...because maybe its not even Reed's Victor and this one is looking at just another poor little Reed that doesn't understand what is going on.
A version of him could be dream walking into specific moments in time (using time slipping logic) so imagine that scene in the trailer again. Doom is booted out of the window and as he's falling, another Doom takes over, lands, and takes it from there. He can re-do every single moment in which a variant of his is losing, and do it differently. Might not even be a single Doom but a whole...council, working in tandem.
Doom takes over Loki's throne (not sure what Loki's fate is but I'm sure it ain't good) and has a direct view of every single multiversal timeline which is how he can see exactly which moment and where to jump into and take over. Each variant he jumps into is a sort of Doombot in that he is operating them all remotely, in a way.
Alright now talk amongst yourselves.