

Because you need network effect. Which means you need big money for marketing, content moderation and development costs. That includes algorithms, which maybe you don’t want, but most people do.
It’s not that I want a for profit company, I just don’t think Mastodon will every achieve critical mass without one.
I’m setting up something similar using Unraid and VMs. This route would probably be more of a challenge for you technically… But if you’re willing to learn, and pay, Unraid sounds like it would be a good fit for what you’re trying to accomplish.