Because an alpaca made a mistake, Lin Shou transmigrated into the Pokemon world. From the start, all he had was a mysterious egg gifted by Arceus and the power of Viridian! A strange world, an unknown environment, and an egg in his hands. Now that's exciting, right? When it comes to catching Pokemon, he'll take whatever he can get.
A Caterpie? That'll do.
A Magikarp? That'll do too.
Life really is one giant amateur production! As Lin Shou put it: Arceus, I'll bet you an egg!