It is certainly possible that the mother purposely left the baby there with the full intention that she would be dead when she came home. But I also wonder if based on her habit of leaving the baby unattended in the past with no consequences that she thought it would turn out fine. Did she expect the grandparents to return home within a day or so but they changed their plans? Did she text a neighbor or friend that she was leaving and expect them to go care for the baby? Obviously still completely inexcusable behavior and the mother is responsible for the child's death, but I do wonder if she carelessly assumed that someone else would just take care of the baby while she was gone like they apparently had in the past.