Simply put, this chunk of the electorate doesn’t have any kind of grasp on the workings of government. As you say, their motivations for voting are simplistic and difficult for campaigns to reason about because they’re so particular to each individual.

Part of the reason why political media has seen such a decline in quality is because of that fundamental lack of understanding by the people. Neutral nuanced analysis doesn’t resonate because that’s some combination of too incomprehensible and not entertaining enough, which has led to the media landscape we have now where it’s turned to the televised version of junk food: hyper-processed with lots of salt and sugar and practically zero nutritional value.

That said, to some degree I don’t place fault on the people for this. A lot of it comes down to inadequacies in the education system when it comes to civics, wherein young people are not well equipped to become highly functional, fully conscious voting adults.