Facebook was not hacked by Cambridge Analytics. Hacking implies that CA broke into their data or otherwise circumvented Facebook somehow to get personal data on 5 million Americans. What actually happened is far, far worse.
The system worked exactly as designed. Facebook is in the data collection and sales business. Somebody created an App. on Facebook for the purpose of collecting data, and it worked. The Obama campaign did the same thing in 2008 and 2012. The difference is that Obama's campaign followed the rules, and Trump's campaign lied, cheated, and stole.
When the Obama campaign ran surveys or whatever the user was always very aware they were taking a survey from the Obama campaign, and thus giving data to the campaign. What happened with Trump is that CA hired a third party to run an "academic research" project that made no mention of its connection to the Trump campaign. The data was collected under false pretenses. Further, Facebook's terms of service forbid selling collected data to other parties. Only Facebook can sell your data to third parties! This entity hired by Cambridge Analytics sold all the collected data back to them, and that is how your personal information got to the Trump campaign. What do you call the act of selling something you don't have the right to sell? One word for that act is theft.
So what do you do about this? Well, you can quit Facebook and delete your account. You Aunt Erma that thinks Facebook is the Internet is probably going to miss you though. Make sure you call her once in a while. The reality is a few hundred thousand or even a million well off Americans quitting Facebook is not going to affect them at all. Also realize that having the realistic ability to quit Facebook is something only those of us living in relatively privileged circumstances have. In many parts of the world, Facebook effectively is the the Internet, and the only way to be engaged in the digital world is via Facebook. People like your Aunt Erma may have the resources to quit Facebook, but it doesn't mean they have the desire.
Facebook is too powerful and has too much influence over our lives for simple consumer action to make much of a difference. This situation is what government was invented to handle. If only we had a functioning government in America.