Author's thought process:
"Make mc weak at the start and become op later."
"Let's give him a trash skill."
"Wait if it's too trash he can't become op later then."
"Let's give him a trash skill but actually op instead."
"Pull reasons out of ass to explain about how trash the op skill is."
"Put it's not like everyone is an idiot in that world, right?"
"Let's just dumb down the world's average IQ except the mc's main party."
"Make mc weak at the start and become op later."
"Let's give him a trash skill."
"Wait if it's too trash he can't become op later then."
"Let's give him a trash skill but actually op instead."
"Pull reasons out of ass to explain about how trash the op skill is."
"Put it's not like everyone is an idiot in that world, right?"
"Let's just dumb down the world's average IQ except the mc's main party."