>>716408452
It's neither too hot, nor too cold, so you can have agriculture throughout the whole year, which is the basis for civilization. If you get one or the other extreme, you're basically forced to move places and it'll be unlikely for permanent settlements to develop, which are necessary to make advanced technological and societal progress.
Latitude doesn't really matter as long as the geographic circumstances allows for the right kind of (predictable) weather and temperatures for farming, but it just so happens that it's the most likely in that zone.