Why would religions spread?

Answer 1

Because back when many civilizations had almost no clue about science, fear, theory, and confusion mixed to create stories and fables. These fables were most likely spread across the civilizations and were later organized by many "holy" people. These organized stories and fables were believed by so many that religion was born. Since religion comforted people from everything they thought was to be feared of and the fact that back then there was almost no means of recording history it spread like wildfire creating discourse over what one civilization believed and what another believed. Because of this discourse wars for what one person thought and what another thought between civilizations began and as of such made those civilizations that lost those wars be forced to be ruled by the winning civilization and convert their old faith to the "new" faith.

In short Fear+Confusion+Theory+People+Organization=Religion+Disagreeing Religion+People=Discourse+Organization+People+Religion(Can be substituted for Vengeance or Ambition)=War

People who win war=Being able to control the people who lose including making laws to make them believe in their religion.