Evolution doesn’t make deliberate, strategic choices. Random mutations result in new behaviors/properties that may or may not be beneficial, and selection removes those mutations that prevent reproduction from the gene pool. Not every mutation will be beneficial, but as long as it’s not harmful enough to stop reproduction, it can persist.
If there were two groups of octopuses, one with the self-destructive behavior and one without, then there would be pressure from competition. In that situation, your point would have more of an impact. But without that pressure, there’s nothing to drive the selection. And the mutation won’t occur just because it would be helpful for it to do so - it’s random.
At least, that’s how I understand it. I’m not a biologist or anything.
I suspect the responses you’re getting stem from the original phrasing:
The question has an implicit claim that there IS a point, which people are rightly pointing out is not necessarily the case (as you have acknowledged). It certainly is an interesting question to wonder if there could be some benefit anyway, so it would probably have helped to frame it that way.
Not saying anyone is required to meet any kind of bar in the level of discourse in a casual online forum, just an observation of cause and effect, for what it’s worth.