What I don’t know is the process in which these radicals came about.
A lot of these radicals came from hieroglyphs. The characters are usually classified into 6 categories:
  1. Pictographs
  2. Indicatives
  3. Compound ideographs
  4. Loangraphs
  5. Phonographs
  6. Signs
Check out this Wikipedia article for details. https://en.wikipedia.org/wiki/Chinese_character_classification