This visualization exemplifies a few interactive design good practices. For instance, if you search for a country, a black outline appears in front of it. This outline remains visible while you play with the time slider, allowing you to focus on that country. Here's Japan:
Moreover, when you hover over any country, a time-series stacked area graph appears, so this visualization also applies a principle described in The Truthful Art, and that I also explain to the general public in How Charts Lie: when a topic is complex, we can't expect that a single visualization will suffice; instead, we may need to encode the same data in multiple ways, as each of them may yield different patterns or trends.
Bloomberg's mosaic plot is part of a long story that showcases other charts, and that discusses how energy production and consumption have varied in several countries in the past few decades. Don't miss it.