Yeah luck was involved, but Microsoft was at least smart enough to buy a company with a good looking game which had been in development for a while. This brought down the timeline. Bungie had showed off halo at MacWorld and was initially targeted at Mac (with an expected port to PC).

Google could do this, or pay even bigger $ for a timed exclusive from a AAA publisher. Instead google started their own studios, which would likely pay off in the long run, but google doesn't have the attention span to operate like that.