Why is this a cult Well I would say it's a cult because you are born into this belief and you don't get to choose and that once you are old enough you must complete a vision quest. After this quest you must take your vision to the elders for them to interpret
Why is this a cult pt. 2 And how do you know the elders are giving you what the spirits said they could just give you the role that they want you to do. These groups also do sacrifices and they hurt the weakest to give as an offering to the gods to get a good crop year a lot of rain good hunting, etc.
How was it formed It was formed when the natives of the land where there and built their own way of doing this and when some thing went wrong they thought that the gods were angry at them so they sacrificed the weakest at first and when this didn't change anything they thought if they sacrifices the strongest it would get better so the strongest started getting sacrificed
How it was formed pt.2 So after the strongest got sacrificed the weather was good and crops grew twice as much that year so everyone shall this and said its the new thing and it was a sign of honor for them to get sacrificed they were all being mislead and this I how it was formed
The reason it's a cult conclusion It was cult because of the fact they were all being mislead by these elders and the chief because they made them believe that sacrifice the strongest to get better crop and weather, and the vision quest is still used today to scam people of money and the person just makes up random things about what they shall