According to wikipedia, Open Philanthropy was founded in 2017. I would've thought that suddenly becoming billionaire-backed would lead to a big jump in the amount of funding being deployed, but when I look at plots of funding over time I don't see any.
Why?
Firstly, from the plot that you link (at least the one on the right) there actually seems to be a clear jump (total in 2017 is 300M from 150M the year before).
Secondly, I think the main reason is that Open Philanthropy didn't just come into existence out of nothing, they started a partnership with GiveWell in 2014 (as the Wikipedia article says as well) and Good Ventures have already been giving through that, so it's not that suddenly a new funder was there in 2017, it's that a funder has been easing in over a long time and the founding of Open Philanthropy as an organisation was just one step in this process.
Cool, yep. This checks out.
Thanks!