Apparently the Heli was flying at 130kts just below cloud before the eventful left turn , and a lot of comment suggests 130kts is a bit fast in those met. conditions .
Im thinking the Pilot felt he was running out of time to get his VIP to destination ontime , and may have been going faster than desirable , and took a chance on getting through on the 101 highway route , because of the earlier substantial holding delay south of Burbank , and subsequent routing north of Van Nuys .
Could pilot have questioned Burbank ATC a bit more about his holding delay , or the unexpected routing north of Van Nuys , rather than just accept it ? , and then maybe bought himself some time for options later ?
Heli could also have continued West on 118 towards Camarillo in maybe marginal VFR ,or climbing above the layer and then IR approach to Camarillo , or had he already decided after passing over Van Nuys to then aim for a set down somewhere near Mamba destination Thousand Lakes to give the pax an on-time arrival ?
We may never know , but hope to learn !