The “Saints” were thought to continue to have thr power of God in them, even in death. Therefore, a Church containing a “holy” relic would have the power of God himself. The saints were thought to be one step closer to God than the ordinary person, so by their relics, those who came in contact with that alter, were extra blessed or empowered by that saint.
If one believes in such things..........
The power of God must have diminished a whole lot then, because we are not seeing anyone capable of raising g the dead, healing amputees, being transfigurated, walking on Water, etc these days. At best all we see today are people possibly being hea.ed in response to prayer in ways that are perfectly imljne with natural possibilities. Nothing super attractive,, ike should happen IF the power of God truly resided in churches in the same fashion that His power resided in the apostles.