I have spoken to quite a few bulls about this over the years, especially knowing they can get laid anytime they like, but spends their times seeking married wives instead. Most even say it becomes quite addictive and they struggle getting excited fucking single women, no matter how hot they are. Firstly, it forbidden fruit, her married pussy is meant to be off limits, yet the rush of violating that rule, makes it hard to give up. But also, there are alpha males everywhere in society, but don't think there is anything more symbolic of showing this to another male, than unloading his seed into the wifes pussy of the other submissive/ passive male.
Also, one bull said to me once after fucking my ex-wife, its like getting to drive my much loved, prized classic car, he's comes around, takes it out for an hour, redlines it in every gear, then just tosses me back the keys when he's done.... without the worry of upkeep, insurance, servicing, lease repayments... thats the owners (cucks) responsibility. I did understand from that, why bulls become addicted to married women as well.