Why did the rise of dictators cause concern in the 1930's

The rise of dictators like Hitler, Mussolini, and Franco caused concern in the 1930s because it led to the spread of fascism throughout Europe, collapsing democratic governments (as was seen in the Spanish Civil War from 1936-39). In terms of American history, this was especially a concern as it caused worry that democratic countries were at an extreme risk. Let me know if you need any more info!