Then why doesnt everyone in the other cinematics die aswell.
PRETTY SURE NAUT AND GRAVES KILLED EACH OTHER AND DRAVEN GOT A FACE FULL OF THE KITTY CAT 
(also good job riot: you deleted my previous post "If miss bitchtits killed GP..." for being "low effort" Id love to have a red reply on why me questioning your reliance here is low effort, your mods are fucking retarded)
DrShoking1 votesin the cinematics they're fighting on the rift so if they die they'll respawn.
Arcade Andrew1 votesThe "New dawn" cinematic might be the rift however the "twist of fate one" you see Ryze and nocturne fighting in some kind of a desert (for sure not the rift) And ryze traps noc then blasts him presumably that should kill him
also according to your theory of re spawns, currently bilgewater is in aram where re spawning is a thing
IE GP should be alive
Marthian1 votesNot really clear if Nocturne was truly killed because he isn't really human, he could just manifest somewhere else.
Arcade Andrew1 votesNoc couldnt escape the rune prison, if he had the ability to he would have, the rune prison clearly trapped him and noc got blasted
and there isnt any proof the new dawn cinematic was on rift, could be but it looked more like a random forest to me (no indicators that is was rift like baron was in twist of fate