Octopus senescence isn’t a choice. It’s a fully programmed part of their life cycle. There’s a bunch of hormones released by the optic gland that put them in this stage where they stop eating, stop healing, and sometimes even mutilate themselves.

For the mothers, the entire time is spent cleaning and blowing water over the eggs.

It’s generally accepted this behavior is the necessary pair to their high aggression and cannibalism. It’s likely if they didn’t go through this they’d end up eating their babies. By dying, they make way for a new generation. And this is their reproductive strategy. Live a short very active life. If you survive, mate, then die and leave the hunting grounds to the next generation.