Thing is, with a consul or triumvirate system (you can’t have more than one “dictator”; all of these terms are from Ancient Rome anyway so let’s use them properly), if any disagreement arises between the 2 or 3 leaders, it will develop a new instability where there wasn’t one before. Or else, one of the 2-3 leaders will start to dominate the others. Even without turnover the dictator system is more stable. In fact the only benefit of a consul or triumvirate system might be the stability and continuity under turnover.