The various people who work on the fediverse are all doing it for fundamentally different goals, solving different problems, and building different things for different people. It just so happens that, more often than not, a lot of our stuff works together now thanks to the hard efforts put forward by people who cared about interoperability.
I personally believe that the fediverse will kill traditional social media platforms. Because if you can just communicate around a walled garden, what's the point or value in staying in one?
I think we still have a long way to go in terms of usability and design. Those things, along with marketing, remain pretty steep barriers to adoption by people who are unfamiliar with it. There are also a lot of capital-H Hard problems that need to be sorted out down the road, like better filtering and moderation tools, and more robust controls for privacy. I have a feeling we'll get there, but only through hard work and collaboration.
I guess a different way of understanding things is that, the fediverse might not kill the competition outright, but it has the potential to outlast them as something better. And hopefully someday, it'll be as ubiquitous and ordinary as email.