It's not free, but it's pretty cheap. When you don't have to have massive marketing departments, huge management bonuses, expensive office space, crappy proprietary software, and massively scaled highly available platforms it costs a lot less to run a social media platform. Donations can often cover it all.
If one server gets too big, they can just cap registrations and people move to a different server.
No, it will never have ads. If the devs put ads in, it will get forked. If server admins put in ads, they will be defederated. That's nonnegotiable if you want a free (as in libre) fediverse.
Mastodon is way bigger than Lemmy and it doesn't need ads. Donations and subscriptions (for severs that choose that path) are enough.
The New Zealand Social Media Study did some analysis of fake news during the '20 and '23 election campaigns. They did a bit more in 2020, here are some of their results: https://www.wgtn.ac.nz/hppi/psir/psir-research/election/facebook-campaign-communication
Except they didn't interrupt voting. Go and watch the video, Maipi-Clarke clearly gives TPMs vote before the haka started. The fact that the report claims they interrupted voting clearly shows how bullshit the process was.
I think it's you who are on your high horse. Claiming there needs to be some kind of "decorum" over a bill designed to strip rights from Maori is utter bullshit and frankly racist.