You cannot expect to understand how and why things work from FCC, i don’t think it’s their intention at all. You are expected to study outside of what FCC offers if you want to learn these things in more depth.
The idea that “even the best programmers google” is valid, but not in the sense that i often see used in here and in other beginner-friendly communities. Of course you should google if you don’t know something, but if you don’t know how the tools you are using work, you can’t really expect to be very productive. That’s something no college, course or book can teach you by itself, you have to actively pursue understanding of what you don’t understand. Not only for programming but any skill in life requires that.