Typora killer? I think that's overstating it a bit. I'm sure more than a few people using Typora (or who might use it) don't have the complex workflow that the author has. Some people only want to write something simple like articles or blog posts. Using Obsidian is a bit much for them. They probably won't use a fraction of Obsidian's features.
Anyway, why does everything need to be the killer of something similar? Can't all these apps just exist beside each other?