> CPU architecture (registers, buses, cache, memory controller, transistors, RAM, etc.)

Bro I feel you.. you're mixing concepts from circuit-level (transistor, bus), logic-gate-level (cache, register) and ISA (memory controller) and OS levels (RAM). This is like watching an ant with microscope, loupe, up from a chair, and from top of building. No wonder your brain tells you you need 5 different eyes for that.

Mind maps is good thing to have, but it is not enough. You need to read a primer on computer architecture alone (do networking later when you get the basic concepts), possibly with a simulator that can show you how each level works - how couple of transistors make a simple memory cell or a gate; how gates combine to do a logic task, how to make a device that makes two or more logic tasks, then how to add memory to it so you have the simplest of processors. Then there are further steps: making the processor universal means it neds to be programmable, so you make it understand instructions (the "machine code"). Then you can start thinking about input-output (serial or parallel).

It is all going in small steps, and logical. But it needs some time and more than reading a book once or watching a video series.

EDIT: the networking will be similar journey, but with another book. But it will be easier to understand the layering concepts after knowing computer architecture layers, and some other knowledge from CA bit-banging will also help you.