A quick version of the explanation of these oddities is that the New Testament appears to include references to at least 3 different views of the afterlife. The Old Testament seems starkly empty of something that should have been a primary concern (especially if they spent 2 or more centuries in Egypt, where the afterlife was all important!).
Josephus has some famous discussions where he compares and contrasts the views of the Sadducees, the Pharisees and even of the Essenes.
Generally speaking, the Pharisees see resurrection as tied to a body of flesh, and that while waiting for the End of Days, the soul is “sleeping” in repose either in or around the last location of his/her physical body.
The Essenes were prone to beliefs in a non-material existence of the Soul, and that the Soul (of the righteous anyway) would wait for the End of Days in a regular waking mode (presumably sleeping and waking in some regular fashion) in an island (“of the Blessed” in Greek parlance) separated from the living by an uncrossable river or ocean.
The Sadducees (families of the High and “highest” Priests) were said to believe in no afterlife at all, except in those few cases where God bodily took someone to his realm (Enoch, Elija in the whirlwind, maybe Moses - because nobody could find his grave).
But I have pondered whether the High Priests secretly thought that only the Highest Priests were interesting enough to God to privilege the families of the High Priests with an afterlife… and everyone else just disappeared.