One possible explanation for that: the visualizations are only useful to those strongly motivated to learn the material itself (as opposed to doing well in a cl

One possible explanation for that: the visualizations are only useful to those strongly motivated to learn the material itself (as opposed to doing well in a class/test or whatever). So, they may not be effective when casually presented to a group of relatively disinterested students—but they may be the perfect thing for some autodidact browsing HN.