Regarding your notion of "there's nothing there to identify" which I assume means there's nothing to the work of Cambridge Analytica.
If that was true then Cambridge Analytica would not make any money. The fact that Cambridge, and facebook, make money, and a ton of it, can make you relatively certain that they can influence people.
No, I'm referring to the idea that the Brexit vote wouldn't have come out as it did absent, essentially, a conspiracy.
That said, plenty of firms make money despite not actually doing as they purport to do. Perhaps Cambridge Analytica and Facebook and the like simply have yet to be exposed as charlatans.
Even if Cambridge Analytica was not necessary for the vote to come out as it did, what they are trying to do still does matter. Because they or someone else is definitely working on improving their techniques, and they will be used in any number of elections to come.
Facebook makes money through simple commercial advertising - nothing sinister there.
Cambridge Analytica might just make money by convincing fools that they have some secret insight or power, when they actually don't. Psychics and mediums have in the past made a ton of money, as did quack doctors. Coca-Cola started out as a quack cure-all and it still makes a ton of money today.
The basic narrative you're pursuing here is one that has cropped up a lot in the past 18 months: voters are, by and large, easily manipulated putty who don't have real reasons or analysis behind their decisions. Instead they simply do whatever shadowy Russian conspirators make them do through subtle manipulation of Facebook, the press, or whatever.
Simple, obvious explanations for what's happening in politics are staring us all straight in the face. Occam's Razor guys ... there is no need to go full chemtrails and pin responsibility on some invisible evidence-free conspiracy of random firms, people and countries. Just assume voters are on average, of average intelligence, and thus probably have reasonably straightforward reasons for doing what they do.
If that was true then Cambridge Analytica would not make any money. The fact that Cambridge, and facebook, make money, and a ton of it, can make you relatively certain that they can influence people.