-- Winemaking, to include the education, mostly from UC Davis, to growing, to actually making it with all the stuff that goes into that: trellising, irrigation, abundant sunshine, etc. I'd say the two biggest reasons are UC Davis training of winemakers and the California climate which is nearly perfect for wine grapes.
So why is the fruit-forward style so popular? Because you can drink the wine now. Almost nobody takes wine home and puts it in a properly temp-controlled cellar for a few years.