https://www.blacktowhite.net/members/allanbradl.47920/
" There is no such thing as preference for monogamous relation. However, there are constrains: moral, financial, social, spatial, etc."
I think you've been buried in way too much cuckold porn. Who says that most marriages fail because of infidelity? Lots of reasons why a marriage fails. The fact that marriages have declined or that more marriages are failing is
NOT directly tied to infidelity or a woman desiring multiple sexual relationships. Society has made getting OUT of a marriage easier, and singles to cohabitate, with less character damage. The majority of women aren't running around in secret screwing any man they wish to screw. Maybe our male sexual fantasies wish to believe that, but that is just not so, and there's no data that says otherwise.