I have known of one couple who are still happily together after both left their marriage partners. There were no children involved though.
They were both so horrified that they had left relationships via an infidelity route that they both went to counselling to ensure that they wouldn't ever be unfaithful to eachother. They were as fair as possible to their former partners, walked away with nothing financially, came clean asap so that the deceit was not longstanding and only married after they had been together for several years and were sure that they would never individually walk that path again.
I know of many more couples I'm afraid, where one or both of them is constantly looking over their shoulder wondering whether a minor problem in their relationship will lead to infidelity, normally because there were numerous lies about how ghastly the former spouse was and the awfulness of the first marriage.
Second partners always want to believe that the infidelity was caused because of relational problems, when infidelity is much more complex and normally points to individual flaws or lifestyle vulnerabilities.
The first couple I mentioned do not regret their union, but bitterly regret the way it happened and have said publicly that infidelity is never justified. If they had their time again, they would have pressed the stop button and tried to resolve their marriages without deceit. The ripple effect for them of hurt and ostracism within the extended family nearly broke them and the stress was overwhelming.
Whereas the person who believes that infidelity is acceptable in some circumstances and especially if the relationship is bad, inspires no confidence at all and it is no surprise then when at the first sign of trouble or lack of attention, they re-enact the behaviours of the past.