Some people are simply not satisfied with maximizing their own gain, they also need to minimize everyone else's. Someone else's benefit is their loss. To the point where they'll make the game negative-sum in order to ensure The Other loses.
Some people are sadistic cretins who revel in the suffering of others, but I don't think that is the mainstream position.
I was pushing back on the idea that "homo economicus" or mainstream economics advocates for competitive sabotage. I have never heard academic economists advocate for this as a rational position.
If anything, the field is biased to over-emphasize positive collaboration.
The position of the parent post is some strange application of group competition for a scarce resource to happiness.
It assumes that someone's goal is not be be as happy as possible, but rather happier than others. This is the only situation where it makes sense to actively put in work to make other people more miserable.
