These guys are making $24k per month on Patreon, for example: https://www.patreon.com/Kurzgesagt - I would guess it's just a function of their audience size and the amount of work they put into fundraising - actually asking people to contribute.
ElementaryOS have actually been working at this a little bit (unlike almost all other open source projects) - and they've built up to $1k a month on Patreon: https://www.patreon.com/elementary - plus ~$200 a month on salt/bountysource, plus direct donations, etc...
These guys are making $24k per month on Patreon, for example: https://www.patreon.com/Kurzgesagt - I would guess it's just a function of their audience size and the amount of work they put into fundraising - actually asking people to contribute.
ElementaryOS have actually been working at this a little bit (unlike almost all other open source projects) - and they've built up to $1k a month on Patreon: https://www.patreon.com/elementary - plus ~$200 a month on salt/bountysource, plus direct donations, etc...