The blog posts from Aras are a really good starting point: https://aras-p.info/blog/2023/09/05/Gaussian-Splatting-is-pr...
Even this article suffers from the same issues? Just in the first few paragraphs: what are spherical harmonics? I read the Wikipedia article but it all went way above my head. There really needs to be a maths-for-smart-but-not-math-phd-people resource.