Several different artsists are responsible. I bolded the groups that I think are most responsible in their generation for the growth of K-Pop.
1st Gen - TVXQ, Baby Vox, hot, god, Super Junior, Fin.KL, BoA, SES, Big Bang
2nd Gen - Wonder Girls, SNSD, KARA, T-Ara, EXO, Beast, SHINee
3rd Gen - Twice, BTS, Blackpink, Seventeen, NCT, GOT7, GFriend, Mamamoo
4th Gen - Ateez, aespa, (G)-Idle, Enhyphen, TXT, Itzy, Stray Kids, IVE, New Jeans
I didn't bold any in 4th gen because it's too soon to tell although IVE, New Jeans, TXT, & Stray Kids would be the most responsible imo at the moment.
Overall out of the ones that I've listed here's my Top 10 ranking of who I think is most responsible, but none of them account for more than 5% of the broader Korean wave. In my opinion, the broader Korean wave is built off successive generations with each one contributing more than the last, but without the initial 1st gen the Korean wave would've never existed.
1. Wonder Girls
2. BTS
3. SNSD
4. Blackpink
5. god
6. BoA
7. Big Bang
8. TVXQ
9. Baby Vox
10. Twice