After that it's just inertia, it's the head of the pack because it's the head of the pack and people already use it.
To convince people to change generally you can't just offer the same or similar performance and features, it has to be a worthwhile reward for the user to bother. This change which just might be crippling enough for adblockers may be enough to get people to switch.
https://www.mozilla.org/en-US/about/governance/organizations...
I'm also afraid how this usually turns out is the for-profit part takes over the non-profit part. See OpenAI or just about any major national non-profit in the US.
Inclusion of Pocket in Firefox is a representative example - included despite overwhelming community objections for more profit!