Here's why:
* Joey Development: Grey kangaroo joeys are born extremely underdeveloped and spend their first few months in their mother's pouch, where they continue to grow and develop.
* The Pouch: While the joey is in the pouch, it is connected to the mother's nipple and receives milk.
* The Pouch is Not Always Safe: The pouch can be a risky place for the joey, and there are several factors that could lead to its death. If the mother dies while the joey is still dependent on her, the joey will also die.
* The Mother Dies from Exhaustion: In some cases, the mother kangaroo dies from exhaustion after giving birth. This is not always the case, but it can happen.
It's important to note that this is not a common occurrence, and most grey kangaroos live long and healthy lives. The death of the mother after giving birth is usually a tragic result of unfortunate circumstances.