Gibbon notes Constantine's late conversion as being particularly convenient because he had one or two of his sons executed not long before he converted. The baptism washed away those sins and rendered him a new man, able to enter heaven without those sins inconveniently dragging him back to the other place.
Edward Gibbon "Decline and Fall of the Roman Empire" was strongly anti-Christian so we need to consider that bias in his comments.
He would fit right in in academia today!