Why are JEE Advanced toppers picking IIT-Bombay over NIRF rank 1 IIT-Madras?

Well, that is pretty easy to realize and analyze.

• The NIRF Rankings System is not the only ranking system, and indeed, it is not even the most widely accepted one.
• Ranking systems consider a lot of criteria such as international students, international faculty, research, etc. which are quite irrelevant to a student taking up an undergraduate program.
• The JEE system has been in place for a while, and students have always preferred IIT Bombay over other IITs. And students simply follow the ongoing trend.

Being said, it’s not true that JEE toppers don’t opt for IIT Madras. If you do a little research, you will find that many top-ranked students choose IIT Madras over the years for their studies.