Keepass is actively developed but uses .Net so Linux requires mono. So KeepassX was created to use C++ so Mono is not required but the project is inactive. So

Keepass is actively developed but uses .Net so Linux requires mono. So KeepassX was created to use C++ so Mono is not required but the project is inactive. So KeepassXC was created as a fork of KeepassX for the linux users who don't want an ugly MOno version of Keepass.