I think education, ideology, and sensationalism have more (everything?) to do with it.
The only big difference between Fox and other networks is that they have way less college educated viewers as a percentage of total viewers.
Not sure how good of a source that is, though. There's several (not great) sources online I can see that say the average FOX News viewer is >65. I also see that the average CNN & MSNBC viewer is >59.
But according to that POS survey, only 20% of viewers are >65 - which must mean a significant portion of their viewers are REALLY old like 80+ (or the surveys are just bad).
538 gives POS an A- for polls: https://projects.fivethirtyeight.com/pollster-ratings/public... - which is pretty good. So who knows?
There's probably no real way of knowing exactly why Fox News has the viewers it does. We can only guess.
A major part of Fox News’ business model is built around creating FUD amongst senior citizens. They seem to be very successful at it.