In addition, a lot of people find that being feminist and being pro-life, or being feminist and opposing divorce, are mutually exclusive and thus it would be easy for anyone wanting to hold the latter positions (pro-life, anti-divorce) to be forced out of the liberal cultural conversation. Once that happens, I suppose most people end up feeling more welcome amongst traditionalist/conservative groups, and that slight selective pressure compounds over the years into the weird social mess we have today.
Sort of, yeah. And the parable of Richard John Neuhaus illustrates that intelligent Christians had to choose -- buy into liberal orthodoxy regarding abortion, etc, (even while disagreeing completely with subcamps, e.g., atheists) or lose their voice entirely.
That combined with other important factors is probably the answer behind the decline referenced in the title.