> Why hasn't the world coalesced around WebKit?

iOS is not the entire ecosystem. Blink dominates everywhere else.

So iOS' webkit-only restriction is not the reason why Chrome is dominant, right? I was trying to follow gp's logic and failing

Look everywhere else: heavy promotion on some of the most popular web properties in the world (Google Search, Gmail, YouTube, etc.) has put Firefox into a death-spiral and Microsoft gave up on their own engine in favor of a Chrome derivative. There is little reason to believe that the same would not be true on iOS were it possible for Google to get users to switch.

I think that matters because while Chrome has a number of great engineers, it's a single team at one company and the web should be bigger than that. We've seen many examples of a Google-proposed spec which became better with feedback from Mozilla or Apple engineers, and that makes the web healthier overall. One really interesting example here has been with tracking where every browser which Google does not control has a better privacy stance because none of those companies make their money by tracking people.