They're not a monopoly in the strictest sense, but they are extremely powerful. People go to Twitter to see what their representatives are saying. Journalists use it almost exclusively to discover what's relevant. Yes, they're a private company, but when a private company reaches a certain level of influence they become a government of sorts, just not one that owns a standing army.
I think you underestimate the power that social media has. The mass 80% doesn't give a fuck about Mastodon or even leave the domains of Facebook, Google, Twitter, and Amazon. This isn't the year 2004 - getting anyone to use a shitty knockoff of Twitter or the like is always going to be an uphill battle. It's due to a few things, namely an accumulation of wealth and confluence with the mainstream media apparatus that wants access to that wealth by proxy. Go ahead and make your own competitor to Twitter and report back to us in a year. Don't be surprised when the MSM labels it in a way that scares off the 80-90%.
I think you underestimate the power that social media has. The mass 80% doesn't give a fuck about Mastodon or even leave the domains of Facebook, Google, Twitter, and Amazon. This isn't the year 2004 - getting anyone to use a shitty knockoff of Twitter or the like is always going to be an uphill battle. It's due to a few things, namely an accumulation of wealth and confluence with the mainstream media apparatus that wants access to that wealth by proxy. Go ahead and make your own competitor to Twitter and report back to us in a year. Don't be surprised when the MSM labels it in a way that scares off the 80-90%.