If it was strictly a territorial squabble, I think the hippo would have tangled directly with the croc and wouldn't have pushed the impala up the bank. That said, I don't see why it would have any hippo-rational reason to want to protect or revive the impala, either. I wish I knew what it was really doing when it kept gumming the impala's head.

Would be ironic for him to be driving an impala with a tiger chasing after him.