There are more connections between the books than are laid out in that chart though. The Last Hero, for instance, features members of the Night Watch cast about as strongly as the Wizards cast, and other books have minor connections to each other that are simply inconvenient to draw out because they’re far away from each other on the chart.
Rincewind’s stories are pretty much all in the vein of fantasy novel satire, while later books tended more towards social commentary in a humorous fantasy setting, so they do end up being a bit disconnected from the books that come later in the series.
There are more connections between the books than are laid out in that chart though. The Last Hero, for instance, features members of the Night Watch cast about as strongly as the Wizards cast, and other books have minor connections to each other that are simply inconvenient to draw out because they’re far away from each other on the chart.
Rincewind’s stories are pretty much all in the vein of fantasy novel satire, while later books tended more towards social commentary in a humorous fantasy setting, so they do end up being a bit disconnected from the books that come later in the series.