I'm thinking the lion wanted to play or wrestle with the trainer.
My cat, although just a house cat, will play a bit rough with me than he will my wife.
Sometimes my cat will chase me down and jump on my leg so I can wrestle or get rough with him.
My cat won't do it to hurt me, he's just showing me he loves me and wants to play.
I think it's a guy thing with the male cats. If they're comfortable around you they want to wrestle and play rough.
Another thought; the cat knows who the male leader is in a house or dwelling and he wants to wrestle or play rough to see who's toughest (in a playful way).