1. There was once truth and power in true doctrine and priesthood power. There were also incidental, physical artifacts associated with the people alive at the time.
2. Generations passed, people died, apostasy set in. Truth and power was lost due to apostasy.
3. Sincere people yearned for the truth and power available in earlier times. Less sincere people wanted the political or financial power available to religious leaders. Without a restoration of truth and priesthood power, people are left with physical artifacts--relics of the past.
4. Relics--and associated myths wound around them--give solace to the sincere and power to the insincere.
The associated myths can be extremely useful to modern scholars because they lend credence to the claim that that there was once truth and power that was lost and needed to be restored. These myths & legends become stumbling blocks if they lend credence to the superstitious belief in relics.