Yes his death was confusing when seeing for the first time for sure. He did seem to expend *a lot* of his final energy just climbing back up onto that damn rock, lol. Which then led to him doing a lot of disappearing within just a couple moments of one another. Now if RJ *really* wanted to subvert expectations then when Luke climbed onto the rock they would have cut to him looking all trim and clean, holding a cup of cocoa on a posh balcony in Coruscant, eyes closed while he projected himself as a washed up old man on Ahch-To, which was projecting *another* projection onto Crait, lol.
Then the Ahch-To projection could have been all "See you 'round sunset."
Sun: "NOOOOOOO!"
I always assumed it was the projection that killed him.. I mean he looks so beat up and exhausted just to get back up on the rock.
Maybe I am just misremembering what I thought his death was back then and have just accepted the Force projection theory as canon.