I don’t buy this at all.
At least here in the Northeast, it is by far the upper-middle class that have most maintained intact families—and yet you’d be hard pressed to find anyone within those families under the age of 70 who believes literally in the Christian teachings about Christ (as opposed to the teachings of Christ, which would still be widely embraced).
The issue, I think, is that those religions which spread most vigorously in the past are those which teach origination stories and doctrine that are challenged by education and modernity.
Meditation and Buddhism actually fit much more comfortably in this demographic in part because they don’t teach what for many has become unbelievable and in part because they don’t tend to be so institutionally hierarchical, looking as if those at the top prosper from the faith of those below.
Provocative. One thing I do notice about those people, though, is that however secure their own families may be, they’ve been known to undercut other people’s family lives by encouraging social trends that can have destructive consequences.