What was wrong with Cain's offering?

Factual Questions
41

It was all because no one explained to God that the steak dinner comes with complimentary salad bar. He was mad because he thought it was going to be added to his bill.

6 And the LORD said unto Cain: “I didn’t order this.”
7 “And a hundred shekels for an iced tea?”
8 “What kind of robbery is this?”
9 And then the LORD muttered under HIS breath: “No way am I leaving a shekel over fifteen percent for a tip.”

42

To echo the Ukulele man–

I don’t see why Cain was later villified, since did eventually give what was expected.

“You want a blood offering. . . .”