Have you watched the Channel 4 stuff? It's about 40 minutes of your time (so far) and totally worth it. One of the points they make is that elections are driven entirely by emotion, and what Cambridge Analytica did was surgically target emotion to achieve the electoral outcomes they wanted.
Targeting on "daisy" is "people watching Patty Duke."
Targeting on "south united" could be as granular as "men 16-22 within 2 miles of zip 90210 who like sports, exercise and sci fi television."
You're right: at the end of the day, that person has to vote. But at the end of the day, he had to have a reason.