It's a chicken & Egg problem. I run a startup in Pune, and we just don't get good developers here. We are open to remote, and most of the good candidates are in Bangalore.
Many cities including tier-2 cities have a variation of one of those "international" schools that parents seek and there's no significant difference in the quality of education between them.
Apart from the usual cycle of available talent + job opportunities, Bangalore has better weather and location wise it can attract talent from 4 states(these 4 states are major contributors to IT workforce compared to other states) while not being too far from place of origin.