This is what happens when you cross the real world with pokemon.
How do these branched evolutions work?
Oh they all start out as bacteria and fight each other to evolve. It is basically an eevee with 20+ evolutions
That sounds pretty cool! However, Eevee has pretty distinct methods on evolving into its forms, like happiness, stones, location... Wait, am I overthinking this? Hope I'm not being bothersome!
No you are a pro theorist, it is good! For each evolution It depends on current conditions (ex. as a crab, spending time underwater could lead to a dolphin evolution) Because logic thats why XD