Quite literally his campaign invented the tactic of scraping your friends list as a way to persuade voters. The important difference was CA used data that was gathered under the misleading guise of a personality quiz.
Cambridge Analytica had 200 clients. Now not all of those are major elections but CA is also not the only player who's been doing this. Governments and shady organizations have been perfecting media-based mass manipulation for decades/centuries.
https://www.nytimes.com/2013/06/23/magazine/the-obama-campai...