You're probably familiar with the term "fair weather friend," - a friend who is only there for you at good times. As you can probably guess from the translation "fair weather democracy", the German compound noun Schönwetterdemokratie takes that phenomenon and applies it to politics.
A Schönwetterdemokratie is a country that appears to be democratic, as long as there is no crisis. This especially refers to economic crises, but many other scenarios are possible, such as (civil) wars, leadership struggles, national identity crises such as secessions, and so on. Arguably, many of the countries that "democratized" after the end of the Soviet Union (mostly through abolishing one-party states and formally institutionalizing free elections) turned out to be Schönwetterdemokratien.