TiddlyWiki is an amazing piece of software, but it has too many points of friction. The first being that you have to run a local server, which eliminates 99% of users.
Up until recently, most wiki software was modeled on Wikipedia, designed for consumption as a website. As an app, Obsidian can have more freedom when it comes to UI, e.g. multiple panes, tabs, command prompt, etc. All of which can make the experience feel richer and snappier than a website.
That said, whenever someone non-techy asks me what Obsidian is, I always start by comparing it to Wikipedia. People understand the idea that Wikipedia is organized via relationships/links rather than chronologically/hierarchically.
This was not always true. One reason TW became popular was because you could save your data without running a web server on Firefox. Then Firefox decided to pull that functionality, and TW suddenly became a lot less exciting. You could still download apps or use the Github saver, but those were far less appealing than the old approach with Firefox.