What made Darwyn Cooke's three-panel layout so effective?

One of the aspects of comic books that make the medium endlessly engaging is how many avenues of storytelling it affords a creative. From the arrangement of the panels, the way an artist orients a reader's attention across the page, to the use of negative space and layouts that subtly influence a story's pace, comics have no ceiling when it comes to storytelling. Typically, novice comic professionals will litter a page with panels to highlight every action a character makes. However, once they reach a certain point in their career, comic creators learn that less is more. 

One of the most beloved creators to ever enter the comics medium, Darwyn Cooke, used his celebrated New Frontier series to illustrate how effectively a three-panel grid could complement complex narrative themes. In the video linked above, you can check out the channel Strip Panel Naked explaining what made Cooke's use of the three-panel grid so powerful.