I think I pursued the details of my wife's emotional affair for two reasons in particular. First, I needed to know the overall character of their relationship and the details would answer the question, "What, exactly, are we talking about here?" My wife and her AP did not have sex - but the details would tell me how much of herself did she otherwise investment in him...and how much he in her. And the truth is, in an effort to suppress revealing embarrassing details, my wife inadvertently left me with a false impression of her emotional affair that was much worse than the truth - and, I believe, nearly put me in a hospital with a nervous breakdown. It wasn't until I searched her computer two weeks later and found emails between the two of them that provided the details that she was concealing that I began to pull back from the abyss.
The second reason details were needed was to answer a question that my WW didn't seem consider - oddly enough. The affair had been over for a year by DDay and my wife focused on working to assure me that she loved me and wanted to be with me. It doesn't seem to have occurred to her that one of the reasons I needed and wanted the details was to answer the other question: After this affair, do I want to be with her? The details will very much inform that consideration.
BH, 5+ Mo EA, DDay 3/8/18
"...regarding all as God after God."