You're ignoring the fact that, originally, deno wanted to eschew the concept of an import map entirely. They weren't against the format of package.json itself, or even against the fact that it's not a web standard. They were against the idea of having to specify imports sepeartely from your code, and against the idea of bundling multiple files into a concept of a module.

Fast forward a few years, and they are now adding these two things natively to deno, just as the web ecosystem did. Turns out, Node was right to have modules and an import file all along, and at worst there were some minor implementation quibbles to argue about.