Why was he kidnapped? Noone entirely sure, it was evaluated differently. Kouffa can lose as much as he can gain from the act. As the leader of the opposition Cissé was against the negotiation the government had with him, this could be a reason. But Kouffa proving himself untrustworthy with this act could hamper in the very same conciliation - playing on the hand of France, who wants to continue the war.
One detail also spices up the act. Both him and Cisse are from the Peul people, an ethnicity native to Sahel, whom are suffering from considerable stigmatization due to the fact that disproportionately many recruits of the JNIM and the ISGS are from this folk. While Kouffa tries riding two horses simultaneously by showing himself as a Peul community leader and a regional jihadist commander, he could suffer a blowback from behalf of other Peul leaders.