I love how the article asks "why?" when humans are an apocalyptic plague on their entire universe.

In the case of the orca this is an easy question to answer.

Its for the lulz.

Given how orcas were wearing dead fish hats for a year or so, then abandoned the practice entirely, "for the lulz" isn't necessarily wrong.

Do orcas engage in an equivalent of intertribal warfare?

If not they might not even have instincts for group defense or retaliation (except in the context of one off encounters with predators).

Not all-out warfare but there can be inter-pod skirmishes. They also hunt in groups and communicate the movement of their prey to co-ordinate their attacks together.