NotebookLM has a mind map feature that organises content from your sources into branches. It can help when you want an overview of a subject before going into the details.
The map does not have to be the only reasonable arrangement. You might discover that two things connect differently, or that something important is missing. That reaction itself can help you understand the subject better.
Treat the map as an initial suggestion to think with. Afterwards, try drawing a small version of your own on paper. When you choose what belongs in the centre and which branches are needed, the structure starts to become yours.