Opinion: Proximate causes

The Californian insurance regulator prompted an interesting
discussion in Insider Towers earlier this week.
For those who missed it, the Golden State watchdogdeclared that property insurers must treat mudslides in areas
burned by recent wildfires as a covered peril for homeowners if the
fire was judged to be a "proximate cause" of the
subsequent slides.
How could the fires be considered the proximate cause of the
mudslides? Surely the proximate cause of the mudslides is the rain?
No rain,...