a lot of people that have gone through NDE (near-death experiences) do say that the spiritual world is much realer than this world.

Many whom consume drugs, specifically psychotropics/ hallucinogens, say the same thing about their "trips". To me, this is almost self-evident, by reason alone.

Why?

Think about it: what feels more "intimate" than being completely locked-up and/or absorbed within one's own mind? Of course that experience is going to have a different quality to it than having presumably near half of your conscious processes focusing on how to best adapt/ react to the objective environment. Of course everything that happens within those moments that all the powers of your mind are focused within the conscious processes/ processing(s) are going to feel "closer to oneself" or less "alien" (more familiar = realer), in general. Of course you're going to discover more about yourself in these types of moments than when your mental energy is more fragmented (doing a million and one things besides observing mental processes and their "symptoms").

NDEs and many of the hallucinogenic trips have one very important thing in common - they completely close off consciousness from the "other" (the world). Left to itself, presumably with all the energy that it had before (when it was in constant observation of the world), many things about oneself suddenly become more focused and intense (vibrant). It's like a "super-amplified" self-observation, all the "self-observation power" of hundreds of hours, in the "awake state" of consciousness, rolled up into a single moment!