wherever the investor sees money.
It's a whole bunch of cities in Punjab though, in Sindh Karachi outshines the entire country though.
For the rest of the country, well there are a significantly lesser educated people around elsewhere. Also business flourishes where the city is open to outsiders. Karachi, is the prime example of it where Sindhis are a minority. I think theres really no clear majority there anyway. Because it doesn't matter. What matters is business.
Also the access to the outside world helps.
Likewise Islamabad is the natural center point for all foreigners and Lahore being the cultural hub.
The planners of these cities have done a lot of things right, while the rest of the nation was cribbing over other things.