As someone who's worked on a lot of collaborative technology, I find it weird how most of the interest in collaborative editing is confined to the web. As I understand it, Figma's internal collaborative engine is written in C++ anyway.
A primary thing Figma understood better than pretty much anyone else is how collaboration among different teams (not just design) works in product development.
Collaboration is also much more useful when you're not limited to only working with people using the same OS. Multi-platform distribution is built into web apps, but it takes a lot more effort to create good native apps on several platforms.
Also, of course, no need to install anything on the web, which is important for frictionless collaboration.
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It's no surprise that both desktop and mobile OS-s are very much not optimized for cross platform development. It's a feature (for owners of those OS-s), not a bug.