It's difficult to explain extremely powerful things. Most times, the explanations you see are either "look - magic!" or ten layers of understanding deeper than what you believe is possible to understand.
So, when you do see a great explanation, you remember it.
Tom MacWright, of MapBox was nice enough to give a talk on D3.js in 2013 at the DC JQuery Users Group. After working with D3 a bit more, and checking out his awesome chartpipe library, I revisited the talk.