The funding is from investors who are Kagi users. You could sign up to be a part of their next funding round if you want.
Public trading means clear protocol for ROI and it allows to have many small investors who can have as little say as you specify (non voting shares etc). Comes with requirement for a lot of documentation and transparency too. So accountability. If business I like wants to grow and needs money this is the route I want it to take
You don't need to organize fundraising events etc you just do your thing and if you do it well you get extra money.
But of course it is all assuming Kagi cannot profit enough from is users. Which apparently it cannot.