It's not just about having the biggest reach, though.
I've noticed that some of the folks who are generally against defederating, whether it be between independent fediverse instances or from large companies, seem to have this impression that fediverse needs to take a huge chunk of some market share in order to compete. But the whole point of the Fediverse is that it doesn't need to compete.
It's not a company looking to increase their size, following a bottom line, and trying to increase profitability. It's a network of people who communicate and share content. There's no need to compete with anyone in order to accomplish that. We're doing it right now regardless of whatever else exists out there.
We've gotten so used to this model where there are only a few really culturally relevant social media sites, but that's literally because we've just bought into the business model of these companies as societies. Slashdot has been going strong since 1997. Is it the biggest forum or news site on the internet? No. It gets a tiny portion of the internet's traffic. But that's plenty to be what it is!
The fediverse is not facebook or twitter or reddit, and it shouldn't be. We don't want or need it to be.
I heard someone make the point recently that nobody walks into a nice, small restaurant and says they wish they were at McDonalds. Facebook is the McDonaldsification of the internet. Let's be a bunch of small mom and pop restaurants instead.