Here's the rule on ejection. The guy was way out of bounds when he gave the last push, and yes I have played sports too, and I was aware when I was out of bounds. If the guy had made an effort to not administer that last hit, I'd have sympathy for his case. But he gave that cute little push that sent the player into the cart, it was deliberate no doubt about it. I'm not saying he intended to push him into the cart, but it was a deliberate cheap shot that placed that player in danger.
"By rule a flagrant personal foul is a rule infraction so extreme or deliberate that it places an opponent in danger of catastrophic injury that it results in an ejection."