In "The Lottery," why are the people of the village willing to turn on their friends and neighbors because of a lottery?
Why these seemingly normal villagers would behave in such a brutal way points to several themes in the story. They participate in the lottery because it is a tradition in their community so old that no one can remember exactly when it started. They blindly follow this custom simply because they always have. No one thinks independently; no one challenges tradition; no one stands up against the majority. It is an example of "group think."
Once the stoning begins, another element enters the story. The people become a savage mob instead of a group of individual neighbors and family members. The psychology of the mob takes over; the mob functions as one entity after a victim has been identified.
The various themes in the story are explained in detail in the eNotes references shown below.
it was the way that these people were raised and how they grew up. like the lottery is something that is tradition we see that even though they dont know why they are doing it they still do it. the rules of the lottery is to stone the person that wins no matter who it is, the parents are teaching their kids how the tradition goes by making them help stone the person that won. the kids grow up that no matter who wins family, friends, or lover they learn not to break the rule but do what they have been thought to do.