As for how those early zombie apocolypes started...
Nobody knew what the fuck a zombie was. People just saw these weird looking drunk guys... and got bit that way.
After that it was a pack mentality type thing.
Or at least that was how Night of the Living dead worked.
Suddenly there were these murderous cannibals all over the place. With so many... eventually a giant mob is going to be too much to push away.
They stopped being a problem once the army and really even just people with guns figured out what zombies were and how to deal with them.








