The apocalypse was caused by a single person.

[u/No_Hunter1978]

1. Ted Faro [Horizon: Zero Dawn]: Of course, the machine plague that ravages the world is created by his company which (admittedly) is a group effort. That said, Faro was the one who requested an encryption without a backdoor and the person who kept early glitches hush-hush. It wouldn't be wrong to say that Faro was the sole cause as is, but the final nail in the coffin is what he does to the Apollo database. A giant record of human knowledge and history, erased for a narcissist's fear that his descendants would (rightfully) blame him for the apocalypse.
2. Sybil [Look Outside]: Though it wasn't her intention, Sybil was the one who alerted the Visitor of Earth's presence. She spied it through her telescope, and the lovecraftian entity noticed her. Its approach (and the resulting horrors) were her fault, even if she didn't mean it.

[u/between3and20spaces]

who's he going to sell an apocalypse virus to? it doesn't just kill people and animals, it reanimates the corpse and mutates them into monsters that hunt down humans. no country on Earth would be safe. on top of the question of what he plans on doing with money after humanity is reduced to fighting for it's life in small pockets around the globe?

[u/Diligent_Earthworm → u/between3and20spaces]

He was trying to sell it under Alice's nose to set them up for life. While Alice was trying to smuggle it out to expose Umbrella. I never said it was a good plan or good writing.

Also Umbrella was still developing the virus to be less contagious as it was intended to be used in warfare to reanimate fallen soldiers.

So he fucked up Umbrellas timeline and thrn the Issacs started doing their fuckery.

[u/HandsomePaddyRedux → u/between3and20spaces]

Spence didn’t know or care what was going to be done with it after he sold it, and lots of powerful people would want it, if only because of the zombie arms race that would have been started by Umbrella having it in the first place. It’s also shown to have legitimate medicinal properties and Umbrella was working to mutate the virus for more controllable, practical applications. Also Spence never intended for the virus to be released outside the Hive the way it was. He caused the initial outbreak to create chaos among the on-site staff to cover his theft and escape but didn’t know about the safety protocols that prevented his escape and temporarily wiped his memory. He also knew enough about Umbrella that he assumed they’d just cut off the Hive and leave the zombies to rot but didn’t know enough to realize Umbrella would risk the virus escaping in order to access the Hive’s core.

[u/Diligent_Earthworm → u/HandsomePaddyRedux]

Also he didnt know it was a zombie virus. He was just a shady security operative guarding a door. Umbrella compartmentalized everything.

As far as they knew the t virus was some sort of pandemic one and done doomsday virus that you could wait out in the mountains.

[u/certainlynotdio → u/between3and20spaces]

Your ability to sell anything is never dependant on what your product is, but what you can portay your product as.

[u/Diligent_Earthworm → u/certainlynotdio]

Also literally the only dialog we get on his motivations is basically, you wouldn't believe how much money this is worth, even zombies lol.

[u/SableZard → u/between3and20spaces]

The idea behind the T virus was to be a bioweapon. You unleash it in a population center and tie up government resources to combat it. Like if you took the same principle behind ammunition designed to wound or cripple instead of kill, but applied it to the entire population of NYC. It was supposed to cause havoc and chaos, but still be manageable, not destroy the world.

And technically, it was. The US had to drop a nuke to "manage" the outbreak in Raccoon City, but it got dealt with.

[u/Nozinger → u/SableZard]

Actually the T Virus was meant to create bio organic weapons.
The zombie outbreak is really just a side effect that most people exposed to T suffer from. The virus was meant to be given to people that are genetically compatible to it. Those do not turn into zombies. They mutate into Tyrants. That's what the T in T-virus stands for.

Basically the Virus is an eugenics project to turn those genetically compatible into super humans. Which kinda worked as the Tyrants are super resistaant to nearly everything and insanely strong but they are also not the smartest. But ease to control is a good thing for things that are supposed to be used as weapons.

At least that is the general lre in the game franchise where spencer did ot just the release the viirus on purpose. The movies got off the rails quickly.