[pete_b]

Pithy answer 2: because they are economically privileged.

The headline is a broad generalisation, and as another broad generalisation poorer people are more religious and more conservative because they have harder lives, bleaker temporal outlooks and hope for a better life 'beyond'.

[MagnumOpus]

I think your "pithy answer" won't stand up to actuall polling.

Highly educated low-wealth/low-income people tend to be socially liberal and probably skew socially leftist (think postdocs, school teachers, humanities PhDs).

High-wealth low-education people probably skew to the right (self-employed craftsmen, sports people, "old money" heirs).