There are many active 'master' branches at work, and many, many active 'master' branches on Github.
By that measure, the movement to rename every 'master' branch to 'main' has been a resounding failure.
(If you look at the events at the time it sprung up, you could pretty safely say that it was encouraged as a way to distract from the then-current "GitHub is doing business with US's ICE!" hatestorm, and man was it successful.)
If your only active metric is "all or nothing". Sure, there's a few.
But the major git hosting platforms are only using 'main' as the default for new branches, and there is significant enough social stigma for new projects that it's preferred to use main.
I don't have precise statistics, but I would happily wager that even though master was the default for so long that the majority of git repositories that have been contributed to in the last 30 days are not 'master' as the default branch name.
To change a default with such inertia as to completely skew the demographic in favour of the new rather than the status quo: I would certainly merit that as success.