Lets get straight.
Why China can't be interested in factors beyond CPEC in Pakistan.
Because: China is a business-oriented state that is more interested in selling and buying than hegemonizing others. For Pakistan is already a neo-colony of China. Pakistan is increasingly getting more and more dependent on Dragons (PRC) after falling from the jaws of Eagle (US) .

Why is CPEC more than a route to China?
CPEC will not be mere a road to run the wheels on for China.
CPEC will be a shortcut shortening the current travelling route distance of 13000kms to 2500kms to the Middle East along with reducing travelling time from 45 days to 10 days. Very importantly CPEC to China would be a prospect of skipping Strait of Malacca to avoid any interruption and obstacle by US's increasing supremacy in the South-Pacific region.

Why is China interested in Pakistan's infrastructure and so then?
China is interested in CPEC which would be constructed on Pakistan's land; therefore how could China in his 51 agreements with Pakistan ignore interests of Pakistan putting bare his personal interests alone. It is most probably the reason: China is facilitating Pakistan in electricity producing projects along with helping in other infrastructural areas.