As I see the data in those green bars (the chart in your linked article), the chance of your marriage surviving ten years falls with each non-marital sexual partner you had before marriage in the way you might expect if your current partner had to go on competing with all your previous partners simultaneously. If she's the only one, she's the best. If she's one of two, the chance of her remaining the best is 1/2. If one of three, only 1/3 chance that she goes on seeming like the best of the lot, etc. (And substitute "he" where appropriate and note that the same calculus is being applied to YOU, too.)
Of course, maybe the marriage survival doesn't require being the best but just >= the past average or some other variation, but that still leaves a curve dropping in a sort of 1/n Zipf Law descent into too-bad-for-you-ness where the competition with the "ex"es never ends. Yikes.