Earlier quoted context omitted.
It's 20 million lines of security sensitive code. Of course it's difficult to properly fork. The same is true of Chromium, btw.
And yet we see quite a lot of Chromium forks - Brave, Vivaldi and Edge come to mind. For Firefox, the number seems to be a lot lower.
Company trying to make money off of its fork.
> Vivaldi
Company trying to ???
> Edge
Microsoft, who found that maintaining a chrome fork would be less expensive than playing catch-up with their own in-house browser.