"If he eats fish, why does he eat me?"

The baryonyx is a piscivore, it was never intending to eat normal meat unless given easy access to such and preferred to eat fish for nutrients. But once humans came, the once passive creature was tamed and forced to constantly kill dinosaurs and humans that the creature had no interest in eating. After the domestic baryonyx were abandoned by their human owners and set to thrive on their own again, they had a newfound taste for regular meat, which had much more taste variety than fish, and eventually all baryonyx acquired this interest in the taste of non-fish flesh and have become aggressive towards humans and other creatures.

(I was bored this isn't accurate at all)