Konami has explained how the zombies fit into Metal Gear Survive
Konami took to Gamescom 2016 with an announcement that shocked the Metal Gear community, they were developing a spin-off game that focused on killing zombies. Regardless of whether or not series creator Hideo Kojima said he wanted to make a zombie game in the past, Konami's choice for their first Metal Gear game without the creator was a tough pill to swallow.
No one saw it coming.
Konami’s brand manager, Richard Jones, has done his best to attempt to explain what the spin-off is. Speaking with Eurogamer (via PC Gamer), Jones explained that the zombie universe ties into the series thanks to a wormhole. Apparently, a wormhole sucked Mother Base staff into a foreign dimension and that is where Metal Gear Survive picks up:
"When your soldier wakes up, they are in a desert landscape. A very forbidding, foreboding, alien-looking landscape with lots of twisted wreckage and lots of things that have fallen through this wormhole. This is where the co-op comes into this game. You're not alone; there are other people there, and in order for you to survive and in order to be successful, you need to work as a team.
"Co-op is only one of the gameplay mechanics. Obviously, Metal Gear is well-known for its stealth, that is, primarily, what makes Metal Gear. There is stealth in it, I know when you're watching the trailer it's all very action-packed and it doesn't really elicit that feeling, but there will be stealth and one of the really interesting things that we will be exploring and playing with is how stealth and co-op can actually co-exist. We've formed gameplay that that kind of allows and enhances that.”
Wormholes aren't new to the Metal Gear series, they were an unlockable feature for capturing, so it's really not to crazy to see them utilized in another way.
So, now that we know that... we know that. The game has a couple things going for it, despite the upset it has caused, it could actually have good gameplay and it's not being sold for $60.