There is EXPONENTIALLY more land available to grow in CA though. Sure NC may have better soil but how much of that will be given up by the current crops to farm marijuana, especially with the market already established in other states? CA grows over 60% of the nations marijuana. Also NC has the issue with mold in the hemp, because of all the moisture and rain. Something CA does not have a problem with.
That's actually not really to be the case in fact. They have a lot more farm land due to irrigation but once you take that irrigation away then the land turns back to what it was before. The vast majority of the crops grown in California are grown in two locations which are the Central Valley and the Imperial Valley area.
The Imperial Valley has only recently (100 years) started growing crops due to irrigation from the Colorado river. Which if there was no irrigation then it would go back to being semi-arid/desert. While the Central Valley area has had a long history of growing due to irrigation from the Sierra Nevadas.
The prime area to grow marijuana in California is in Northern California due to the higher amounts of rain they receive compared to SoCal. So that is why they have what's called a Emerald Triangle.