Why does the bystander effect happen?
The more people watch an emergency, the less likely any one of them helps.
People are less likely to help someone in trouble when other people are present. The more bystanders there are, the less personal responsibility each one feels.
Someone collapses in a busy station and dozens walk past, each assuming another will act.
Responsibility gets divided across the group, so no single person acts.
If you need help in a crowd, point at one person and ask them directly - it breaks the diffusion.
Many eyes, no hands.
Learn the idea and practice English at the same time.