Because after BTS , Big hit debuted lot of Boy group and took lot of BG from other agency under their wings ( TXT, Enhypen, SVT, Nu'est)
and if BTS success was thanks to Big hit, all these other groups would have reach the same amount of success that BTS did in term of international popularity, and sucess in Korea
But none of them were able to even did well in Korea, and struggle in chart
which logically means that BTS success isn't thanks to Big hit amazing brain but it's just luck
because when you compare with other agency, every time they create a new BG in the past they were able to produce something as popular than their previous BG
SM = HOT - Shinhwa - TVXQ - SUJU - EXO - NCT
YG = BIG BANG - Ikon - Winner ( yes Ikon and winner aren't as popular that they were but nobody can deny that they had a lot of success and even have big hits )
JYP = GODS - 2PM - GOT7 - Stray kids
All the new groups from these agencies were able to break some record from the previous BG of their label
but only Big hit new groups aren't able to do as good or break any record from bts
which can only means that Big hit isn't great at making big groups they only surf on BTS success know and use bts name for their new groups, and luck is a big part of BTS success, because if it was thanks to BH, BH wouldn't have any problem to reproduce the same success they had with BTS with their new groups !!!