Why can the presence of larval stages during animal development be beneficial for the species?

The presence of a larval stage during the development of animals can be beneficial due to:
1) Often the larva and the adult live in different environments, which helps to reduce competition for territory.
Example: the beetle larva lives in a soil environment, and an adult (imago) lives in a ground-air environment.
2) The larva and the adult eat different foods, which helps to reduce competition for food.
The larva of the May beetle feeds on the underground parts of plants (root systems), while the adults feed on the aboveground parts (stems and leaves).
3) + The spread of individuals of the species in different environments increases the habitat, which leads to biological progress, and therefore a greater stability of the species.