The roots of the movement lay in the 1920's when the first Congolese visited Paris, and returned with dapper suits.
“Sape is French slang for “dressing with class”. The French often use the expression “il est bien sape” to talk about a sharp dressed man. The term “sapeur” is a new African word that refers to someone that is dressed with great elegance…Nowadays, more that ever before, it is necessary that the Western (or Northern) countries, as the dominating culture, redefine their role in the world and recognize and acknowledge the consequences of their model of development for the rest of Mankind. This model, based on an unsustainable growth maintained by over-the-top consumption patterns, is what the rest of the world looks up to. On the surface, this model seems to be a paradise. The media and the immigrants returning to their countries, keep the myth of the Promised Land alive. In this process -consciously or not- our values tend to become myths, and therefore are considered superior (or more advanced, which is the same thing) to the traditional values of other cultures. Although this process has been greatly accelerated in recent times, the problem goes way back, and in the African case, to the times of Colonization. In this context, I reckon the Congolese Sape to be an evidence of the nonsense and terrible contradictions of our model of development.” -Hector Mediavilla, ‘The Congolese Sape’, artist statement
BBC made an interesting documentary about Sapeurs, you can read the interview with the makers (more here):
BBC Four: As your documentary shows, the members of La Sape are fiercely devoted to designer clothes. Could you elaborate on the symbolic importance of high fashion for the sapeur?
George: The Sape emerged from the chaos that was the Congo during the reign of Mobutu. It was really one way of coping with a society that had broken down. For a young person growing up at that time, there wasn't much to grasp hold of to help you feel better about yourself. Politics was out, so you found a lot of cargo cult religions in the Congo. The Sape is essentially one of these. The distinctive look of the sapeurs was also a rebellion against one of Mobutu's dictatorial decrees, which was that everyone was expected to dress in a very traditional, standard African costume - the abacost.
Cosima: The sapeurs in Paris and Brussels are using these European status symbols not to integrate into European society but to 'be someone' back home in the Congo. This separates them from European fashionistas. They aren't so much concerned with proving anything to the outside world but rather to one another, among their own community. These people have grown up with no kind of social structure to rely on. The Sape is a mini-state providing its own social strata: president, ministers, acolytes and so on.