Why did they do a 180 in their car and cause the crash in the first place?

I have no idea. I just finished it and I don’t know wtf the end was about. I thought those people branded her as some kind of victim for their morbid religiosity or but the end is telling me they were initiators of her crashing only and any explanation of the actual branding is dropped from the movie? I understand why I see so many worst movie threads here.