The main difference is that manhwa doujinshi are often created by fans and are not officially sanctioned, while regular manhwa are produced by professional creators or publishing houses.
Maybe it's because the story or art style doesn't appeal to as many people. Sometimes, the promotion or marketing for a manhwa can also affect its popularity.
Chinese manhwa often have unique cultural elements and storylines based on Chinese traditions and values. English manhwa might focus more on universal themes and have a different art style.
Tumangaonline manhwa often has updated content more frequently and can reach a wider audience. Traditional manhwa might have a more established fan base and might focus more on the quality of the physical publication.
Well, it's hard to say for sure. Coincidences in manhwa can either be simple plot devices or part of a more complex web of events. It depends on the context and how the story unfolds.