It could be that there were technical problems or not enough funds to keep it running. Sometimes, changes in the market or competition can also affect its fate.
Often, such sites face legal actions and get taken down. Maybe that's what happened to this one. It's important to note that these kinds of sites are usually not in line with proper online behavior and regulations.
There are no ethical or positive sites dedicated to such stories. Cheating is a serious and often hurtful topic that should not be exploited for entertainment. Instead, you could focus on reading relationship advice or self - improvement books that promote healthy relationships.
Another option could be Archive of Our Own (AO3). It's a large fan - fiction archive. There are a lot of different story categories, and some of them might involve stories about cheating wives. However, it also contains a mix of different types of content, so you need to search carefully using relevant tags.
You can download manhwa apps that offer offline reading options. Some popular ones include Webtoon and Tappytoon. Just make sure to check their settings for the offline feature.