I don't intent this to be mean to Deno, but did it ever really get traction? Hard to describe something as a decline if it never really held a significant position.
Maybe at some point. Their vsCode extension has 1M downloads, while Bun has 155k.
That might be because Bun doesn't need an editor extension. It has type definitions and works fine with the built-in TypeScript language server, formatter, etc.