Even a person who has mental disorders or has been in a coma is very clear just before they die. That person is turning loose of the physical body which has held them captive for so long and is living and speaking from their spirit man. For a few moments before they slip over into eternity, they can communicate clearly with those remaining. Often when a dying believer says they see a departed spouse, relative, or friend, those present explain it away as senility. They explain that the ones they are speaking to and speaking of have been dead for many years.
Senility is the first answer our natural mind can find to explain what is happening.
But I believe the Word of God gives another explanation. I would have expected it to say he was gathered to the Lord or to a company of angels. But instead, Abraham was met by a group of people he knew. David joined a group of believers who were spiritual heroes before his time. As David slipped over into the realm of eternity, he was met by those he revered, whose lives he had studied.