I have to admit, diagrams are a bit harder to do in text, especially interconnected graphs.
That said, I could imagine something that uses triples to define a rendered graph, similar to how RDF for the semantic web works. Say
#BEGIN_GRAPH
'Paul Graham' founded YC
'Sam Altman' leads YC
YC funded AirBnB
YC funded Reddit
AirBnB <> Accommodation
#END_GRAPH
Leads to a graph like [Paul Graham]----founded----->[YC]------funded----->[AirBnB]<------>[Accommodation]
[Sam Altman]-----leads------->[ ] `---->[Reddit]
Now that could be prettier, but I am too lazy to copy and paste box drawing characters.
With a simplified form like that, all the data is in the form of subject predicate object sentences, which makes for easy parsing. The data could also be fed into a diagram making application like yED for pretty graphical output.
Maybe "reading" is a low tech invention that we just don't have the patience for anymore. Instead we want to "explore" a theory or network of statements or social graph.
It's pleasant to click around in Wikipedia and get a sense for how different topics relate, but reading the (often turgid and boring) prose seems like work.