There has been some speculation about how the chemistry of the brain changes during near-death, which can cause these experiences, but there is no proof of that.

However, there is an almost universal change that takes place among people who experience near-death: they don't fear death anymore. It's hard to imagine how such a common, specific change in attitude could be attributed to random brain chemistry changes.

And if these experiences cannot be attributed to anything physical, then the unavoidable conclusion must be that something metaphysical is happening.

nobody can say for sure especially not me lol... but I have done a lot of research on this topic and read countless experiences/studies etc. i've wondered the same thing - why when some people die they say it's just like going to sleep, and for others they have experiences involving encounters in a whole other realm?

the only thing that's made sense to me regarding this is that, it is whether the person needs this experience to change something in their lives or not. I strongly believe this realm people go to when they have an NDE is real, and I think that before you "enter" your earth life, things that are going to happen throughout your earth life are decided there. this is why some people are told about future events, which are then confirmed to happen when they come back from the NDE. (this particular aspect of NDEs, in my opinion, also rules out any speculation as to whether NDEs are real or just illusions. if it was merely an illusion, there's no way that could happen.)

NDEs are ALWAYS extremely life-changing for the people who have them... in every single case I've read, anyway. so I think the NDE is necessary for the person who has it - to change the way they're living their earth life/feeling inside etc. it's not to say that people who die and are revived without having an NDE are living perfectly or something, but maybe it's not their soul's time to have that awakening. hopefully that makes sense.