I agree that is not black or white. I know a number of couple (including my father and SM) who went through the pain of an affair, made it the other way and became stronger as a couple afterwards. An affsir is also not always one sided and although always wrong, the reasons that led to it are often two dimensional.
There is also staying by fighting and working through the crisis rshter than accepting and turning a blind eye. There is also self-preservation.
If a couple has grown apart, staying mainly by habit but with a shared love from a satisfying element of companionship, just no intimacy (in all form) nor friendship, some will be happy to stay together with one turning a blind eye to an affair, the other turning a blind eye to the fact that they are expected to continue to support both financially and it can work.
Or, it's the outcome of a crisis that requires work to get back on track. It can work too if the issues are resolved.
However, if the woman choose to pretend it's not happening despite feeling massive anger and resentment, but stays purely to benefit financially because a comfort lifestyle and financial luxuries are more important than self esteem, than this is likely to end badly.
Whether to remain a sahw or go back to work is always going to be a risk to assess. It's wonderful to stay at home enjoying a life of leisure with just a few hours to do housework with the full freedom of time, but this comes at the price of dependency and the risk of losing a lot or all if the marriage collapses.