system
Given the following post, respond as if you're commenting on Reddit:
human
[DBS] How come Beerus didnt know who Majin Buu was?

When Beerus meets Buu for the first time, he seems to think that its just some fat pink guy who wont give him pudding. 

Yet, buu is millions of years old, and almost killed all the kais, which would have killed Beerus. Even freiza and his dad knew about him, how come Beerus didnt knew about the extremly old being that almost killed him five million years ago? If nothing else, Whis should have know who he was, unlike gods of destructions, the angels are never said to be replaced, so he should have been there atleast.
gpt
Because Beerus is a temperamental slacker who naps for decades or centuries at a time. He probably slept through the entire massacre of the Kais. And as long as Shin survives, so does he. 

When he woke up and discovered what happened, and that Buu had been 'dealt with', he probably just chastised Shin for being careless, and stormed off to gorge on some mediocre food somewhere.

He's also shown himself go be easily distracted, and forgetful, so even if he HAD intended to destroy Buu should he be released, do you really think he'd remember that after millions of years?

Frankly, Champa is the only God of Destruction that seems even more incompetent than Beerus.