True, I was ignoring the distinction between the supply of shitty web pages and the supply of attribution-recording advertising opportunities provided through them. Not quite the same thing even if they do seem likely, as you proposed, to be closely correlated in the scenario where Mozilla’s product somehow ends up surviving to become a hugely influential new ad platform.
https://theyesmen.org/sites/default/files/styles/max_width_850px/public/2020-11/hallib-whatnoahknew-Slide33.jpg