I really don’t see how it killed him. It was super draining, I don’t dispute that, but I see it as him peacefully becoming one with the Force. Rey even says Luke’s gone but that it was with purpose and intent.
Are Jedi supposed to disappear when they die? The OT suggested so, but the PT explicitly says otherwise.
Why specifically did Yoda and Ben Kenobi disappear? Did Yoda disappear because he died peacefully, or did he disappear because he purposed to give himself over to the Force in his final seconds? Did Ben Kenobi disappear because because he sacrificed himself at Vader’s hand, or because he gave himself over to the Force in the instant before Vader could kill him?
The question about why Obi-Wan and Yoda disappeared but Qui-Gon did not nor did any other PT Jedi ever (or even Chirrut Imwe from R1) has never been answered.
Maybe Luke disappeared for the same reason Obi-Wan and Yoda did, but the OT doesn’t explain why Obi-Wan and Yoda did.
Not saying this was the right way to explain it, but Force spirits were explained in the last 3 episodes of The Clone Wars Season 6.