We've elected/voted-to-confirm judges since statehood (according to info I found on the matter), so it's how our government was set up from the beginning in California. The process has changed over time, but it's a core aspect of our democratic system. Some judges we elect through vote, while other judges are proposed by the Governor and then comfirmed or not confirmed through a vote.
As I've said before, voters have a lot of power in California. We can recall (force a vote on whether or not to remove an elected official from office) any elected state officials, including judges (though we've never recalled a judge). Citizen-groups can gather signatures and propose amendments to the State Constitution without ever involving elected representatives. They can also gather signatures to force referendums on legislation passed by elected officials.