Q: How did the “Assumption of Mary into Heaven theory” come about?
A: It’s more than a theory. It’s an official dogma of the Catholic Church, and one of only two Ex Cathedra, infallible statements ever proclaimed by the Pope, throughout the history of the Church.
There are a number of valid theological reasons for the Assumption of the Blessed Virgin Mary, as well as earlier scriptural precedents for it in the apparent bodily “translations” of Enoch, Elijah, and possibly even Moses.
It is known from scripture that Satan spared no effort trying to locate and claim the dead body of Moses, as some sort of a “trophy” … finally being frustrated by the concerted efforts and strong rebuke of Michael the Archangel.
Knowing this, if you were Jesus, King of Kings and Lord of Lords, triumphantly returned to Heaven after your successfully completed mission, but knowing full well that Satan, while officially powerless, still remained a dangerous fugitive back on earth, how long would you permit Satan to have his way with your own mother?
Then there’s the traditional explanation:
A number of the apostles witnessed Mary’s apparent death. Her body was placed in a tomb, and several days later, the tomb was found to be empty, her body seemingly replaced by a huge volume of flowers.
Some time later, St. John received the Book of Revelation from Jesus Christ, and John correlated the images and events in the last part of chapter 11 and the first part of chapter 12 with the events surrounding the “dormition” of the Blessed Virgin.
Based on this, the Catholic Church has always understood that God would not allow the sanctified flesh that was used to fashion Christ’s human body to see the corruption of the tomb. And since Mary, by special privilege of God, was necessarily sinless from conception, and further sanctified by some 34 years of dwelling in the immediate presence of Christ himself, there was absolutely no need for Mary to await the resurrection, since according to God’s grace, Mary had absolutely no sin that would warrant divine judgment … or death … for that matter.
The Church authoritatively and dogmatically explains all of this here, much better than I have, complete with extensive citations:
But this short excerpt from the above document sums things up pretty well:
40. Hence the revered Mother of God, from all eternity joined in a hidden way with Jesus Christ in one and the same decree of predestination,(47) immaculate in her conception, a most perfect virgin in her divine motherhood, the noble associate of the divine Redeemer who has won a complete triumph over sin and its consequences, finally obtained, as the supreme culmination of her privileges, that she should be preserved free from the corruption of the tomb and that, like her own Son, having overcome death, she might be taken up body and soul to the glory of heaven where, as Queen, she sits in splendor at the right hand of her Son, the immortal King of the Ages.(48)
And as St. John explains at the end of his gospel, there was indeed a whole lot of very significant, authentic stuff going on, that never made it into the Bible.
Believe it … or don’t. (Catholics are required to believe it.)