.. is that, maybe things happened the way he thought they did at that moment but that in a situation where there is a complex problem between two people, one action, whatever it is, isn't going to be a permanent solution. Hurt feelings and anger and so on will crop up again some other time and have to be dealt with again.
Your situation was not as much like his as you think. You drifted almost accidentally into what you term a "cyber affair." Yet had you not confessed it, the issue would have been solely in your own mind and a struggle with your own conscience. So it wasn't really a deep seated problem between you and your husband. You didn't commit any physical infidelity, and this was a one time episode that snuck up on you. I agree, whatever action was taken to alleviate your guilt and give you an incentive not to return to this "affair" was very likely to work.
My situation was in between the two. It was physical. It was a one time thing also spurred by the fact that my boyfriend was away. But he was told about it by another person and so there was anger and hurt pride on his part. And so the spanking didn't solve it. It kept cropping up. Not on my part because even before he spanked me I already knew I was done with the other guy and would not continue the outside relationship. The problem kept recurring on his part, he was unhappy about what happened and he kept bringing it up every time we had a disagreement.
And that's on a much lower level of complexity than a situation where a spouse committed adultery over a 13 year period, the marriage dissolved and now they are together again. The spanking has cleared the air but my prediction is, the issue is not dead and it will be back to trouble them.