Actually, you can take the ideal form of the plasmoid and demonstrate mathematically that this is the lowest-energy state. More generally, it has been proved mathematically that the force-free filament is the lowest energy state for current moving through a plasma and the plasmoid is the lowest energy state if there is sufficient helicity (twist) to create it. In other words when the twist gets big enough, the plasma drops inot the more stable state. This mathematical work was done back in the 1950’s.
