id co-founder John Carmack today revealed that the change of the name was due to an enterprising domain name squatter.
"This was an idea we had mere weeks before QuakeCon," said Carmack, emphasizing the freewheeling nature of the Quake Zero announcement.
As it turned out, the speed of the game's unveiling came back to bite the company, when a quick anonymous individual purchased the Quake Zero internet domain names.
"They offered us a considered buyout option for it," added Carmack. "We just decided heck, we're only a few months into development of this, we'll just change the name."

Maybe that an Quake 1 and 2 being nothing alike.
Hope he likes his useless domain now. Glad they didn't give in to it for any amount.