-Small population

-smallish electorate with restricted franchise

-multiple levels of electoral colleges and overlapping legislative and executive bodies to spread, balance, and obscure power

-relatively small number of families dominating at any one point and, somewhat less typical of the form, many of the same families dominant for most of the thousand year history of the republic

-tight focus on key interests combined, often enough, with cunning opportunism and flexibility

-emphasis on a sort of cursus honorum for the elite, with exposure of future leaders to commercial, naval, military and administrative duties

It all worked very well at small to medium scale for a very long time. Mainly overcome by larger scale changes in the demographics, economics, and administration of larger states.

But OTOH, the republic also had started to stop working all that well a good few centuries before Napoleon finally toppled its corpse.

Of course, that’s not necessarily a black mark. No state or institutions are eternal.

That sounds rather stupid. If you can’t predict which candidate will win, simply bribe them all. Happens all the time.