The whole art of missions and conversion is a complicated one...
Centuries before Freud and his psychology, Church used tons of symbolism, propaganda and mental influence to ensure people WILL believe in God.
For example, roman-style churches usually had very long main hall, which was dark, and altar, bright and lighted by solar rays coming through windows. People walking through church were heading through darkness toward light - like from path of sin to the God himself.
Also, another commonly known thing is "poors' bible", illustrations which shown scenes from evangelies. This way, even those who couldn't read could know Bible the way Church wanted them to know it...
Also, art pieces, like "Temptation of St Antony". It shown St Antony, sitting in forest, while all around Devil was tempting him - and not Devil shown like in testament, great, powerful demon - but rather, small and hard to see - series of small hands and feet, trying to kill a fat pig in vicinity of hungry saint, or spilling water and wine from the pots...
Also, let's take Cotez' trials to convert aztecs. Aztecs had bloody religion, they sacrificed people by ripping out bleeding heart from their chest, they ate their enemies to gain there strength. Cortez converted them mostly by understanding their beliefs (those, who he wanted to convert, through he simply anihilated most indians on his path); they told them to eat the wafer and drink wine, because these were blood and flesh of God. If Aztecs would gain adversaries' powers by eating them, they would gain power of God by eating God's flesh, won't they? They were eager to perform this sacrament...
