Let me just give a disclaimer for my below comment. I am not a PML-N/NS support. Quite the contrary. I would define my self apolitical-centralist. Bellow comments are also word of mouth from others that I came to hear.
Barring the corruption charges, what I have heard is that NS is not as pandoo or incompetent as you believe him to be. He has on several occasions attempted to be hands-on with things and has sought accountability of national institutions, which didn't go down well the corridors of our state system. In the end, he ended up on the receiving end of the accountability instead of the giving end. He definitely made some enemies in the wrong place at the wrong time.
Anyway, someone from FBR once mentioned in my presence that they collected record revenue during NS's PMship. His railway minister Khwaja Saad Rafique did a pretty good job in reviving the railway. Previously, Bilour had almost wiped the railway out not just financially but administratively also. Similarly, someone from PSO once mentioned in my presence that 'say what you will about him as a person but Ch. Nisar is actually a very good administrator (he was minister for petroleum 1997-1999).' I have seen people who are opposed to PML-N concede that Ishaq Dar is one of the best persons for the finance ministry. As for IK and his team, well, you can see the revenue, currency value, and railway management by yourself. There are things about NS that don't come up on media. I think the Chinese probably prefered him because a) he commanded popular support and b) he had better business acumen and team then others.