Which is not considered a factor of decline under emperors diocletian and constantine?

The factor that is not considered a factor of decline is the reunification of the Roman empire. During Diocletian's rule, it was created a tetrarchy - a form of government that divides power between four individuals, two rulers in the east and two rulers in the west - Galerius and Constantinus. The Tetrarchy made the government gain control again of the Roman empire for some time, but later it turned into a confusion because of the lack of a single authority. When Constantine came to power - he inherited the West Empire from his father, the tetrarchy was abolished, and the Roman empire again was unified under a single ruler - Constantine.