Why did the Roman army proclaim Constantine I emperor at York in 306?

The Roman army proclaimed Constantine I emperor at York (Eboracum) in 306 following the death of his father, Constantius I, who had been serving as the senior Western emperor.12

While the tetrarchy established by Diocletian was intended to provide a structured, non-hereditary succession, the troops’ actions reflected a strong attachment to the hereditary principle. After Constantius died during a campaign against the Picts, his soldiers immediately acclaimed his son, Constantine, as emperor. This act bypassed the established imperial succession process, which had previously passed over Constantine in favor of other appointees. Following this proclamation, Constantine began his rise to power, eventually becoming the sole ruler of the Roman Empire.3124