Its because of the "non-interference" bs policy.
If China doesn't want to interfere, the West will gladly do it. This "take the high road" thing only works out in fairy tales
Interference is a domain. If China refuses to engage/fight in it, then the West will win it and then proceed to damage China.
In this case, IK is very beneficial for China because he has been developing and reforming Pakistan's economy. The stronger Pakistan is, the stronger China becomes.
If the opposition parties (= corrupt thieves) come in power, then this means a weak Pakistani economy which is not in China's interests.
Its all about who can develop Pakistan more. IMO the person who can do that is IK, and as such this is the guy that China should want to be in power