What if Call Of The Dead never exist? Imagine 3 lines of time,
1 is the original zombie story line
2 is the zombie story line but CotD never exist
3 Nothing happen with zombies, Group 935 never exist, so Samantha never controlled the zombies or Richtofen.
So here's my theory:
When we did the Call Of The Dead Easter Egg, we wasnt the original crew, we needed to send them to the paradise( Shangri-la)
So we send them, but, at the Shangri-La Easter egg, we could time travel to the past, but wath if everything we did on Shangri-La change the past and the characters of CotD film the movie,they never kill zombies so the world never explode due the Moon Rockets.
There was another Evil person who controlled them, not Samantha, Richtofen or maybe Dr. Maxis, It was an Evil Force who controlled them, or maybe nobody controlled the zombies because the Red Eyes are the neutro eyes of a zombie.
Another thing that could maybe be right,is that some Evil Force is controlling the ISLAND, not letting Richtofen control them.
Conclusion:
Mob Of The Dead is a zombie story line 3 that Sam or Richtofen aren't controlling the zombies, maybe thean Evil Force, or the zombies by their own. Thats why the earth is not destroyed.
Please let me now what you think about this, this theory may be crazy but theres a chance :)