I guess it's to find the associates of people of interest and which places they frequent so they can spearhead efforts to hack them or their associates and find sensitive data. Like military data or something that can be used for blackmail. Political stuff too.
I don't think it's to gather data on ordinary people. But that can be a side benefit if they happen to find it useful for some random thing. I still can't think of what it would be used for.
For apps and cell phones I believe it's just a thing of money. They want to see which products they should produce in China to strengthen their economy. And to steal credentials.
Other network things might be used to compromise a network.
How much of this is true? Idk
How much of this is technically possible? I don't either know
