One of these doesn't require a multi-decade approval process for good reason. (Figuring out the logistics and civil engineering planning is a real thing and building it out isn't trivial) . Of course this could change

you know there are jurisdictions outside of California that don't take multiple decades to add a bus line, right?

these aren't "good reasons" or unavoidable laws of nature or understandable tradeoffs. it's just a uniquely dysfunctional political system