If it were such a great climate for growing things, they wouldn't be talking about getting fresh water from thousands of miles away.

It used to be a great climate for growing things, a century ago. But that was during an abnormally wet period in Californian history. California is usually much dryer than it was a century ago, and is drying out once again. In California, people think one or two centuries of experience with the land is a long time. In most of the world, that's a joke. Try farming the land for a thousand years before you form such expectations.