You have confirmed the first reason.
"Such efforts require years of design, permitting and fundraising and are not easy to build.'
In other words, the state isn't sitting on the cash.
https://www.kunc.org/environment/2022-03-10/what-does-it-tak... shows that a reservoir in Colorado took two decades to get permitted. The projects in California are moving at light speed in comparison.
"As much clamor as there has been for more storage, however, water experts warn that it may not be the panacea that advocates profess, specifically reservoirs. Constructing reservoirs is expensive, meaning the water they sell may be cost-prohibitive for some, while the increase in water supply is likely to be small and not worth the money given California’s increasing aridity.
"With the warming climate, the state is not only seeing more intense droughts, alongside more intense storms, but more of the precipitation is falling as rain instead of snow. Snow has historically provided a second wind for reservoirs, melting after the wet winter season and giving the lakes an additional hit of water."
"'What you want is reliable supply and this (type of storage) is not very reliable. You don’t know when you’re going to fill it.'"
In other words, the problem facing California is drought depleting snowpacks and groundwater, not "more water storage" in reservoirs.
The world's scientists are in agreement that you're wrong about climate change and doubling down like Pope Urban VIII is just silly and especially sad when you cite an article that disagree with you.