From my studies and experience I’d argue the fourth paragraph nails it.
“Another possibility is that there is a biological or evolved mechanism that stimulates arousal in this situation. Specifically, seeing another man (or multiple men) bedding a desirable woman may stimulate sperm competition. The basic idea is that when such a situation is observed, men’s bodies and brains respond in such a way as to increase the likelihood that their sperm will outcompete that of other men. Consistent with this idea, both men and women report that after a period of separation or when female infidelity is suspected, the male partner thrusts faster and deeper during their next sexual encounter, possibly as a means of displacing other men’s semen.”
The rest is interesting – but our biology and evolution (our true nature, not social conditioning) cannot be ignored.
Yet nature is seen by many as a fetish.
Amanda’s note: Not just faster and deeper, the male has stronger comes – releasing a river of semen from my experience! This is an amazing and very primal thing to enjoy. One of the rare and intense pleasures… but only for the secure elite of lovers. A male who makes love to a woman who has just enjoyed another cock pulses with the desire to reclaim her pussy by giving her greater pleasure and more copious seed with his cock. Pagans understood this well. Today society introduces jealousy and stupid ideas about infidelity… undermining the exquisite cock hardening and toe-curling pleasures of Nature.