I think the misspelling is in large part due to the mispronunciation of the name. 
Kubota (Koo-Bow-Tuh) would be correct. But many folks pronounce it (Kuh-Bow-Tuh) and go on to spell it phonetically 'Kabota'.
I live in rural Deep East Texas, so I am used to hearing all kinds of 'butchered'...