I had a perception that NIFTY is an index, and it's price is derived from the underlying top 50 companies (NIFTY 50).

Which means i can safely assume, that if price of 5 NIFTY 50 company stocks goes up, it in turn will bring up NIFTY index, not the other way round.

But today, on 14th March , i was surprised to see that the underlying NIFTY 50 stocks behaved somewhat exactly the same way as NIFTY (please see the graph in "Today" column).

How is that possible? Kindly help me to understand.