Probably because their presence in Niger is neutral and business related, while Russia is actively promoting anti-terrorism and stabilizing the region. Just my speculation.

Despite China's growing presence, support and approval in Africa, many people there unfortunately still believe or have internalized Amerikkkan neoliberal propaganda to where they dislike or heavily distrust China and communism, and China's comparatively cheaper and altruistic investments and assistance to Africa for very little or no returns can easily be viewed in a suspicious lens.