The Carnotaurs are smart predators—they never attack the herd, instead following behind and eating those that fall to the wayside or stray away. This is the option most predators would take, of course. But after the cave-in, the surviving Carnotaur charges the entire herd, even though it couldn't possibly win against all of them. Why the sudden change in demeanor? Think about it: why do foxes sometimes kill entire flocks of hens? The entire herd, at this stage, was confined inside a small space. At this point, its hunting instincts were going absolutely beserk and, when it was in "kill mode", it was going to kill until it stopped receiving distress signals from prey in its immediate vicinity, rather than stopping and thinking "alright, I got enough to eat with this one".
Charging a herd is also a common predator tactic: the hope is that some will take fright and scatter, which nearly did happen here.
Alternatively, if it had indeed been mated to the other Carnotaur, it could be interpreted as a Roaring Rampage of Revenge.
Aladar managing to challenge the Carnotaurus into stopping its charge is also very much Truth in Television. Predators want their prey to turn their backs and run, but if that prey faces them down (even if its smaller) the predator will be much more hesitant or even retreat. This can be seen in modern mammals, but also birds. Ever seen a small bird absolutely dominate a big bird like a crow or hawk? Same idea.
Notice how Carnotaurs from the beginning of the movie ignores young Parasaurolophus who lured it out of the forest in order to hunt down something bigger. That's because Carnotaurus intended to observe herbivores quietly until a viable target comes close enough to ambush (as a real predator might); but the Para's approach forced it to break cover early.
