A lot of agricultural water usage (more water than AI) is for growing corn to turn into ethanol so we can add it to gasoline. It's not a small amount either, 40% of all corn in the US is used for this purpose.

We use about two orders of magnitude more water (each!) on corn and alfalfa than on data centers as of 2023, and while we're ramping data centers up fast, it'll still be an order of magnitude at the 2030 data center estimates (which may heavily overestimate, now that there's so much opposition popping up).