I was surprised at this too, but I guess there’s more to California than the Hollywood lefty and hippie types that our watered down media usually portrays. I’m not as sure about Washington as I am about Colorado, but the latter state’s governor, John Hickenlooper, is actually one of the most liberal politicians in the nation on any level. He’s also a Quaker, and from my experience they appear to be very enlightened and liberal folks when compared to many other religious groups.
I was surprised with Washington because I had heard that it’s actually a very conservative state, except for the more populated areas. Many pro-cannabis advocates in Washington are still complaining that the police are finding alternative ways to harass folks. I think that Colorado is ahead of Washington on this issue.
My guess though (in answering your question) is that these states had the adequate political support necessary to support what the voters actually wanted in those states without as much red tape. In other states where these issues are brought up, politics usually gets in the way of what the voters actually want, like my question about asset forfeiture law reforms clearly demonstrated.