The Lion immediately eats the cabbage in step 1.

To be fair the puzzle never explicitly states anyone would eat anything. Perhaps the lion simply can't stand the thought of being alone with a cabbage and kicks it in the river.

The key is understanding the constraints and what would be an acceptable amount of bending whilst keeping to the spirit of the game.

It's never explicitly stated that you can't take things back with you so that's your "aha" loophole. Throwing all three of them across at the same time because it turns out you're a giant wouldn't be in the spirit of the game.

Oops, I had "goat eats cabbage" in my head.