Music "Expanded" Universe

Forgive me the strange title.

So... K/DA are the last music-themed skins. So, as far as we know, we have:

• Pentakill band:
• Popstar Ahri: (obviously)
• DJ Sona: (uhm)
• K/DA:

So... A bird told me that all these skins belong to same universe. -----> https://twitter.com/notquitefrodo/status/1059176880991916032 (follow all tweets) Don't wanna complain, but... Doesn't make a lot of sense.

Ok, Popstar Ahri WILL become Ahri from the K/DA and that's ok. Now the strange one: K/DA Evelynn said Karthus to be her greatest inspiration ----> Pentakill same universe -----> Pentakill Karthus (ooh...) Pentakill's version of the land is detroyed (by them) and the landscape is like cracked and desertified. They just destroyed everything and i'm pretty sure Pentakill play in Runeterra. K/DA, on the other hand, play on Earth (they mention Korea and Asia, ecc.).

The Earth became Runeterra, then Pentakill came and BOOM? Is Pentakill lore based in the future? But, if this is the case, why Evelynn knows Karthus? Pentakill are, like Galactus of Marvel comics, cosmic music devourer of worlds, so they just come in and eat (wooooow)? Maybe Pentakill are members who play "music from old" and so, like classical music nowadays, people refer to Pentakill like they were Mozart of our world? But... In the train of the music video of K/DA we see, perfectly, the sticker of first album of Pentakill. Doesn't fit, i guess.

And... Is Sona a DJ or a Keyboardist from Pentakill? Part-time job/Session woman? Ok, Sona is the music character and fits everywhere, but in this particular case? I can admit DJ Sona can play along with K/DA, but...

Mmm