Even large cities have problems with voter turnout in municipal elections:

Voter turnout in local elections has always been low, and it’s gotten worse in recent decades, studies of voting behavior in municipal elections have shown. In most of the biggest U.S. cities, fewer than one-third of eligible voters turned out in the most recent municipal elections. And according to data culled by researchers at Portland State University, those who do cast ballots in major cities tend to be significantly older than the general population, a factor that might weigh against women and candidates from diverse backgrounds.

My impression of elected officials in suburbs is that a good number get into local elections because they care deeply about an issue. With low turnout, relatively small communities, and a lack of formal political parties (many smaller municipal elections are supposedly non-partisan), it does not take a lot of resources to run for local office.

Of course, some of these variables are different at the big city level: often dominated by partisan politics, a larger need for significant sums of money, and a need to woo tens of thousands of voters. Still, it is notable that the leaders of some of the most important cities in the world can be voted in with votes from a relatively small number of citizens. These local leaders may not be able to easily move into national positions yet their decisions affect residents on a daily basis in a way that more abstract and further removed national politics cannot.