Dragon Ball Reborn As Krillin

Why did Earthlings become secondary characters in the later stages of Dragon Ball?

Why do Saiyans and Frieza have such high combat power from birth?

Why does the story focus so much on the confrontation between gods?

Why have Earth's inhabitants been constantly oppressed, with the planet always on the brink of destruction?

I am absolutely not convinced that I've been reborn as Krillin! Just wait and see! I will defeat you scoundrels and protect my Earth!

As a purebred Earthling, I am determined to stage a comeback! Endowed with the invincibility of Saitama-sensei,

I won't act rashly, but when I do, blood will be spilled.