I'm glad you brought up the Roman dictatorship, because it's a great example of the way checks and balances worked in the Roman Republic. There were
nearly 100 dictators prior to the 2nd century B.C.E. - often appointed in times of crisis - and not a single one attempted to seize control of the state. There are probably a number of factors that led to this (the fact that dictators were only granted their powers
within the realm for which they were appointed; the fact that dictators could only last 6 months at maximum; the fact that dictators couldn't legislate; the fact that the tribunes of the plebs were absolutely outside the authority of the dictator; etc. etc.)
> Those checks and balances were simply not needed during peaceful times
There weren't any peaceful times. Almost literally. Rome was at war for all but 6 years of the entire Republic.