The laws of nature say "you need a water system so big to support X population" with California's regular cycle of wet periods and droughts. What "gave" was political will to either continue building out the system or limiting the size of the population fed by the system.

This is just one of many examples where a "can was kicked down the road" for future politicians and the people they rule over to deal with, this mess was made certain in the 1960s. The unfalsifiable concept of climate change has nothing to do with it, except that the climate cycles were well known long ago.

More recently it's been discovered this is at least partly linked to the https://en.wikipedia.org/wiki/El_Ni%C3%B1o%E2%80%93Southern_...

"During El Niño events, increased precipitation is expected in California due to a more southerly, zonal, storm track. During La Niña, increased precipitation is diverted into the Pacific Northwest due to a more northerly storm track."

We realized El Niño was a thing no later than the 19th Century, and per a Wikipedia skim evidence has been found for the cycle going back at least 10,000 years.