What dictates the evolutionary path of a fictional creature like Arbok within its ecosystem?

The need for escalating power within a structured game world, set by game designers

Unlike biological evolution driven by natural selection or automotive evolution driven by engineering refinement, the progression of fictional entities like Arbok is governed by entirely different constraints. Its evolution, a structured progression within the Pokémon universe, is fundamentally dictated by narrative requirements and the rules established by the game designers. This artificial ecosystem allows for rapid iteration and specialization where the goal is often defined by escalating power levels or meeting specific in-game challenges, rather than adaptation to a physical environment characterized by resource limitations or predation threats.