I think it's more of an assumption required by models which say "democracy is a good idea that will work well." In other words, the typical civics class model goes something like "democracy is a good idea that will work well, assuming that (among other things) the public is engaged and well-informed."
That ironically isn't true - it can work well for reasons seperate from good decisionmaking even when excluding incentives as a component (democracy gives a wider array of relevant interests in decision making).
For one democracy is a good pressure relief valve - far from the monarchist fears they were way more stabme compared to the regular secession civil wars of monarchies and rebellions. Election results let a potentially hotheaded minority faction know "you won't win you know, you got only 30% of the vote - let alone what percentage would actually fight for you. You are outnumbered so chill, campaign, and wait for the next election".
