Meh I wouldn’t put too much stock in an evolutionary impulse to kill our children with compassion. A lot of species kill and eat their young during food scarcity because the parents have a better chance of procreating in the future than the offspring, and sometimes animals will kill offspring so the mother has capacity to find a new mate and bear its offspring instead. There are a bunch of reasons why primates kill offspring but none of them are altruistic from the offspring’s perspective: https://en.m.wikipedia.org/wiki/Infanticide_in_primates

I do think people find these particular child murders fascinating because women are generally much less violent than men. When men kill their children it’s just assumed it’s for revenge or some other selfish motive, whereas when women do it society likes to speculate that they are also victims in some sense.