It's a very sad story behind this. How they marketed directly to the DayZ community claiming that their game would be 10 times better then DayZ. Basically trying to over-run Dean Hall, the one man developer of DayZ, who had it very though at the time, with a horde of angry gamers demanding updates.

Dean was basically making nothing developing DayZ because he wasn't allowed to monetize it (because it was a Arma2 mod). While the War-Z team made tons of cache on pre-purchases even before their game had been released.

The War-Z totally deserved the shit-storm when players discovered they didn't even live up to half of all the promises and hype.