[nimithryn]

Also Christianity was a Levantine religion, growing fast in Greece, Asia Minor, Egypt, Syria, and the Levant. The Eastern Roman Empire at the time was far richer, more urbanized, closer to the grain supply, and closer to Silk Road and Black Sea trade access.

Based on some of his other actions (like moving the capital), I'd speculate Constantine's conversion was part of a deliberate pivot to focus on the East (which paid off, as the centralized Byzantine state went on to survive much longer than its Western counterpart). I'm speculating because inferring his intentions has no historical evidence afaik.