Cain, through the sweat of his brow, was really pleased with his fruit & vegetables. He piled them up before God. They must have been really something........remember how it took two Isrealite men to carry one bunch of grapes?
Why did God despise vegetables so much seeing that he had made them?
Any parent knows not to favour one child over another, but what does God do? Yep he does just that, told poor Cain he had no regard for him or his offering.
Oh & God forgot to tell Able to watch his back when around Cain or that Cain was getting mighty upset about the favour I'm showing you.
Seeing they were all supposed to be vegetarians at that time where did the idea of having to spill the blood of another sentient creature to please God come from?