Wikipedia is also just a bunch of numbers, so many that you can't memorize them, you may use the same argument to say we don't know why some page links to another.
If you then put Wikipedia, LLM and Brain on a scale to how well they can be understood, you will see that one of them is not like the others.
What about Wikipedia do you think we do not understand? I would say, mechanistically, we can read the code and explain exactly why it does what it does. That doesn’t apply at all to the other two.