It seems the K-pop industry has come up with a somewhat repeatable machine for churning out these bands: they manage everything from scouting young talent and training them, writing the songs, merch, events, etc?
That's pretty much what every boy band creator does since nkotb in 1984.
The truth is 16 year old boys don't get together with 4 friends and make music like this. So you need someone in the industry to bring talent together, write their songs, etc. Compare that with rock, rap, punk, emo, etc which happens more organically usually.
It's no different to what has been happening in the music industry for decades. Many of the most popular pop songs are written by third parties and the recording companies will often pair artists with experienced producers and tour managers.
The popularity of K-pop is more an artefact of the US mainstream favouring individual rap/hip-hop over dance-centric boy/girl bands and leaving a large opening in the market.
The truth is 16 year old boys don't get together with 4 friends and make music like this. So you need someone in the industry to bring talent together, write their songs, etc. Compare that with rock, rap, punk, emo, etc which happens more organically usually.