> but it's that Cambridge Analytica wasn't Facebook's fault (users willingly granted access), but it was their problem.

In Careless People, they mentioned that this was a strategy they wanted to employ:

They wanted facebook to become a tool for winning elections so that they would have more leverage over the politicians in power.

For example, they were trying to fight the Indian government over internet.org initiative (essentially shipping out a stripped down version of the internet to impoverished areas where they could only use facebook and a couple other apps, subsidized by telecoms). They used facebook features to incite backlash against the Indian government.