It's not even profitable _now_ with all their monetization. But their overhead is millions of $/year. There is precedent for non-profit sites of that size but it won't be easy.
Honestly with the amount of charity fundraising that reddit does, I bet they could pull it off. Just recently someone accidentally gave $15k to charity and in response, a bunch of users raised an additional $55k [1]. If they did intentional, annual fundraising with clear goals I wouldn't be surprised if reddit the non-profit organization could be self-sustaining.
But I'm just some guy on the internet who doesn't actually know anything about non-profits.
I also suspect their tech stack is a huge ball of bloated inefficiencies that costs them much much much more than the bare metal and the bandwidth would.
But I'm just some guy on the internet who doesn't actually know anything about non-profits.
[1]: https://www.reddit.com/r/BestofRedditorUpdates/comments/1456...