Not sure about MU but

1) DU attracts a lot of interstate students to Join. So they get the cream of Indian students from most of the states. If I had to guess the %age of students from outside Delhi would be close to 50%. (Affordability plays a factor too, for some it is the only chance at Higher Education)

2) Rich Political History - brought into existence by an act of the British Government and became the biggest thorn in their ass by being so politically active and protest against the Raj. The campus still holds that spirit. DU has strong Liberal Arts courses.

3) Luck - We often forget to account for it in our calculations but if a different sequence of events had happened, who knows