> and has a singular bogeyman they’re convinced explains all of the problem, with zero room for multiple causation

Not sure about that. But each person tends to have something like a single sentinel flag. E.g.: does medicare negotiate drug prices? And if there's a change for the better, they won't believe it's anything but a short term grift until they read it back as "true" from at least 16 different threads over the course of, say, 9 consecutive years.

Given that their representatives currently use phrases like "medicare advantage" to mean "off traditional medicare and on private insurance," that caution seems warranted.