Ah I didn't realize it. I've never driven through a corn field on California, or I've never noticed it like in the Midwest. And it's all to feed the cows of course.
The "number 2 in sweet corn" is a little bit cherry picked, sweet corn is the corn grown for humans and is just a little bit of the total corn grown (~1%). It's much nicer fresh, so it isn't surprising that a huge state grows quite a lot of it.
The numbers at the provided link reveal the picture, talking about California having ~200,000 acres of grain corn and the US having 87 million acres of corn.
(As an aside, in my limited experience, Europeans might not know that corn on the cob as eaten in the US is always sweet corn, and that modern varieties barely need to be cooked, pretty much just heated through. Methods vary, but just a minute or two of boiling is pretty common.)
