I think Fly.io employees are a lot more active on HN which is why you see them mentioned more often. They also write great blog posts which get a lot of attention here.

I also agree with the sibling comment. I came to Fly.io being sold on servers running close to the users. But I didn't see much of a peformance improvement with my web apps as they all have to communicate with Firebase. There's probably situations where this technology makes sense, but I haven't found a use case yet.