There is a concept in evolutionary biology called parent-offspring conflict.
Roughly summarised it is the tension between keeping resources or giving them to offspring.
At some point, adult survival is a better genetic option than caring for the progeny and so the parent puts their foot down and withdraws support.
This can be a shock to a youngster who has been told his mother’s goat is no longer available to provide him with creamy goodness. Or the lion cub who gets a plate-sized paw to the snout and two-inch canines to a haunch.
It just that time for provisioning has ended and Moms genes are better served caring for the next generation.