How does collecting Facebook user data help Trump get elected? Genuine question.
You use the data to identify people who could be encouraged to vote the way you want them to. You anticipate the hopes and fears of these people, based on the dataset. And then you target advertising at them, based on those hopes and fears, with the intention of encouraging them to either not vote, or vote for your customer.
You could also target their friends, who may already support your customer. Hit them with stories that confirm their existing bias. Encourage them to share those stories. Basically, you want swing voters to drop any thought of voting for your customer's opponent.
In the case of the US election, this could mean identifying democrats who aren't keen on Hilary, who worry that she is dishonest, along with undecided voters who share the same opinion. Target their Trump-supporting friends with negative stories about Hilary, specifically the email scandal, and any other occasion you think you could use to convince people that's she's a compulsive liar. Encourage them to like and share those stories; "get the word out". Then target the identified swing voters with adverts that echo the message they've seen their friends share. You don't need these people to become huge Donald Trump fans. You just need them to become wary enough of Hilary Clinton to not vote for her, or vote against her.
Then there's all of the other stuff; the blatant admission that they are happy to target people with fake news in order to influence opinions. The suggestion that they will run smear campaigns against political opponents, even going so far as to traffick sex workers around the world in order to set up a honeytrap.
Two different issues really. The first is about the business and industry as a whole, and whether or not something needs to be done to reduce the potency of this type of targeted advertising. The other is about whether or not senior figures within Cambridge Analytica acted in illegal and immoral ways in service to their clients.
When it comes to Facebook, I can't help but think people need to be saved from their own lazy stupidity.