RIP. As this was a training mission, I think it is fair to ask why they were flying in and into a major storm, the largest of the season?
I agree. For a helicopter flight all the way from Creech Air Force Base, north of Las Vegas, Nevada to San Diego, with a major major storm in front of them, there were a number of official places they could have set down (including the Marine Cambat Cneter at Twenty Nine Palms) and wait for the worst of the storm to pass. With the storm the issue was not the rain (visibility) as much as the air turbulence and then they also were approaching some low mountains. There was no mission critical need to not set down somewhere safe temporarily, radio in their situation and wait till the biggest part of the storm passed. Their commanders need to take issue with why the Marine team did what they did.