So now that the lore has been released I now see how 
is involved but what about 
, 
, and 
!!!!!! This has left me empty and wondering.... longing for more story!!! GIVE ME MORE STORY!!!!!!! ....Please??.... I'm begging here!
Garen, Vi, and Sona were chosen for artistic reasons -- they looked good in the teasers. This isn't to say that Jhin hasn't been planing "performances" for them.
There's a red response to this on Reddit, should be linked on S@20 if you want to see it
This was asked already several times and even before jhins lore was released,they clarified that these 4 are merely people that jhin knows(he probably heard of garen,Sona and VI while working outside doing some assassinations) and it shows how he'd imagine their deaths.
Overall these 4 were mostly chosen based for artistic reasons and not for lore-related reasons.
Have to say, I called it back when the teasers were first floating around. Same thing happened with Kalista (the fog around champs) which ended up being alot of hype to nothing.
Sona, Garen, Vi and Zed were chosen because they are popular (could you imagine if in Jhins teaser he was shooting Malzahar and Galio?). Zed just so happened to be lore related.
