The video did not answer all my questions. There are a few things I still don't understand.

Google AI says:
Why Hunter-Gatherers Practiced Higher Rates of Infanticide:
In nomadic foraging societies, infanticide was primarily used as a tragic but highly calculated method of population control and resource management, heavily driven by the strict biological constraints of their lifestyle.

The Mobility Constraint:
As noted previously, a nomadic mother could realistically only carry one infant or toddler at a time while traveling miles a day to forage. If a woman gave birth too soon after her previous child (before the older child could fully walk and keep up with the group), the survival of both children—and the mother—was severely compromised.