A simple toroidal magnet creates a complicated field, while this complicated magnet creates a much simpler and more benign field. AFAIK, in Tokamaks you need t

A simple toroidal magnet creates a complicated field, while this complicated magnet creates a much simpler and more benign field. AFAIK, in Tokamaks you need to permanently increase the plasma current to keep it stable, which puts an upper bound on the time you can sustain the plasma (you can't increase the current forever). In a Stellarator, by contrast, you can keep the current constant, and thus have plasma durations measured in hours instead of minutes.