What i don't get about these movies is Umbrella's motivation.
Pretty much everyone is dead already. There's no one to sell their stuff to, there's no one to finance them and there's no one left that they could kill with their bio weapons.
So why are they still in business doing their unethical research thing?
Bureaucratic inertia with a hint of denial.
If the President of the United States survives the complete destruction of life on Earth, he's still going to act like he's the President of The United States, while anyone who manages to survive while working for him or with him will act the same way, even though all of their jobs became meaningless when the last private US citizen got immolated in the holocaust.
Umbrella is still operating and running their experiments just because that's what they were doing when the world went zombie, and even if they have nobody to sell their breakthroughs to, that doesn't mean they can't find a way for themselves to outlast the plague, so they'll keep trying to do that until either the zombies or Alice kills them all.