There are VFR flyways in and around the LA area, but in degrading weather TCAS will only help so much. At some point the pilot has to commit to IFR. VFR to IFR (IMC) kill many pilots. If you've never experienced it, you have no idea what an uncertain 60 seconds that can become. I've heard a report that the aircraft was descending at greater than 2000' per minute. Bottom line, the pilot lost his situational awareness and either pull so much power he drooped the rotor, or he reduce the power enough to enter an autorotational descent. Neither one of those implies good decision making. Bottom line, we'll probably find out he lost his situational awareness and became spatially disoriented. Quite possibly the most uncomfortable phenomenon you'll ever feel. Your body screams one thing, the instruments say the other. 99.99% of the time the instrument are right. If they are wrong, it's usually only one, and you have to fill in the gap with the information from the other. Now, the S-76 typically has some level of an autopilot. But if you put off your decision to land until you can't, then you try to commit to IFR and haven't trained the transition in a while, it can end badly.
In one of the most heavily radar covered airspaces in the US, it's an unfortunate and avoidable loss of life.