Small connection between Garen, Vi, Sona, and Zed.

Each of these champs are generally accepted as being toxic to play against (and I say this as a Sona main), with garen being the least egregious. Perhaps Riot is using the next champion as a lore reason to rework them (the problem being that Garen just received a rework of course), perhaps temporarily killing them?

As the lore currently stands, there is no in-lore connection between their characters, so perhaps there is a game-play reason.

That, or one or more of the champs could be having their personalities changed/expanded, and there actually is lore behind it which we just don't know yet.