Why do we have and thoughtlessly use the expression : "Meteoric RISE to fame"...?

Although meteors do fall, as you say, the the adjective meteoric is not meant to describe a meteor.

It is something swift and spectacular as the falling of a meteor would be. The word meteor is derived from the Greek word meteoros, meaning lofty. Originally it was used to describe any atmospheric condition. Technically to call a falling object from the sky a meteor or meteorite is incorrect but the word has become accepted in common use.

eor

Meteors move at rapid rates. A meteoric rise to fame is an incredibly fast achievement of notoriety or celebrity.

We use this phrase to imply that the rise to fame is "similar to a meteor in speed, brilliance, or brevity."

It is a mixed metaphor that still does not offend our sensibilities. If we visualized a meteor rising we would probably be more outraged.

Also like why did Darwin call his book the "DESCENT of Man?" Are we not ascending from the dark ages?

Because most of us are just parroting words and phrases, so not understanding even what we are saying most of the time!. So where's my imaginary 100 points, Yahoo?! ..Further LOL ...)