In the United States, a grisly story made headlines last year when an 18-year-old former neo-Nazi in Tampa who said he had converted to Islam confessed to killing two (apparently still) neo-Nazi roommates, though that case is so grotesque, and the use of violence so far from mainstream Muslim practice, that it defies comparison to the European examples. (The suspect also shouted a nonsensical, non-Muslim phrase.)

In all cases, the shift from anti-Muslim to Muslim is counterintuitive. One potential factor is the ease of conversion to Islam. One can declare oneself a Muslim after uttering the shahada, with no requirements like the baptism or confirmation needed to become Christian or the process and certification used in Judaism. Someone can announce they are a Muslim without demonstrating any particular devoutness, longevity of commitment, or knowledge of the religion’s precepts. This is not to say than any given convert is not sincere, but that stating someone has converted to Islam doesn’t really clarify much on its own.

These cases of anti-Muslim activists in Europe converting to Islam don’t represent a trend, but there are enough of them to wonder what might inspire such apparently 180-degree turnarounds. When he converted, Buttey, the FN councillor, argued that the far-right movement had more in common with the religion than its members realized. “Both are demonized and very far from the image portrayed in the media,” he told Le Parisien. “Like Islam, the FN defends the weakest. The party denounces exorbitant interest rates charged on the debt of our country, and Islam is against the practice of usury.” It’s hard to imagine many French Muslims accepting a kinship with the FN, but in any case a more fruitful direction might be not to look for what far-right parties share with Islam but rather what forces might attract members to both.

There seem to be some people who are joiners, eager to become part of larger groups. Almost everyone will know someone like this, perhaps someone who is constantly searching for new social groups or joining new organizations, or perhaps even a spiritual seeker-type who flirts with a succession of faiths. The cliche about the “zeal of the convert” exists for a reason.

According to Michael Hogg’s uncertainty-identity theory, people seek to reduce questions about who they are, where they fit in the world, and how people view them. “One way to satisfy this motivation is to identify with a group (a team, an organization, a religion, an ethnicity, a nation, etc.) a process that not only defines and locates oneself in the social world but also prescribes how one should behave and how one should interact with others,” Hogg writes.

Far-right (as well as far-left) political groups benefit from people struggling with such questions. “Extreme groups ... have precisely the properties that are ideally suited to reduce self-uncertainty because they provide a clear and unambiguous sense of self and place in the world,” Hogg and Janice Adelman write in a 2013 paper.