@Ashu Ashu do you remember the tigress demon incident that happened in s1 where she was killed by her own husbands hand and how her brothers were behind incident which was led by the 2 brothers...those 2 were in low ranks at that time to go through a higher rank they much do something worthy enough to be ascended
So the woman dies and her husband goes mad in the end while wearing a lady robe n trying to kill the groom of every wedding happening in his village...in the end he goes totally mad n dies of starvation
This news reaches the brothers n they thought this'll be a big hassle to clean up...they found the man's body n buried it n cursed it(the curse that ryeong n jae eradicatd from the village later)
If a mortal human dies he has to go thru the 10 gates of trial to see his reason of dead n if he is worthy of reincarnation or ascension or whatever so if that husband goes thru that the brothers get caught of will be punished for eternity cause the rule of the heaven is to not meddle with the human life in any way and they did that
But if the husband turns into a vengeful spirit the heavens only focus on eradicating the spirit instead of investigating it so the brothers won't get caught (idk how to explain this)
I think this explains the misdeed of the brothers :')