Question

Why the human suddenly change their behaviour like another human?

Answer 1

that's due to influence , its the nature of humans .They tend the become like them but over a period of time they will come into a realization that they have been influenced and they will eventually overcome. it can be due to various reasons ( they include - like the other person's attitude,they think if they change their behavior they wont get judged(its called trying to play safe) and many more..... )

hope it was helpful : ) !