The map began with an algorithm that grouped counties based on proximity, urban area, and commuting patterns. The algorithm was seeded with the fifty largest cities. After that, manual changes took into account compact shapes, equal populations, metro areas divided by state lines, and drainage basins. In certain areas, divisions are based on census tract lines.
I've lived in Pennsylvania, Connecticut and Rhode Island, and none of them make much sense as states.
This map is presented in the context of electoral college reform, but these states just make way more sense in general. America with these state lines would be a vastly different country, with urban interests fully represented.