The answer is rather simple, if any professional courtesy is acceptable. The Christ (i.e., Messiah) is an overwhelming theme throughout the biblical text.
What the Christ is is still rather confusing, even among so many religious leaders and scholars. Yahushua stated that he had been anointed “The Christ”.
Anointing usually takes place for the purpose of refreshing oneself or for an occasion requiring a solemn oath, like being anointed as king or as a priest.
However, Yahushua stipulated that the purpose of his anointing was quite specific. The anointing of Yahushua as The Christ, which anointing took place at the Jordan River and performed by Yahushua’s cousin John the Baptizer.
Yahushua made the purpose of his anointing very clear. Yahushua did this in his hometown of Nazareth, shortly after being anointed by John. A flare for the dramatic was in order, so rather than a Mikva, John used the river. A bonafide public statement, and an attraction capable of attracting the attention of the authorities and commoners alike.
Yahushua also made the purpose of his anointing very clear, and it almost cost him his life before crucifixion. To make the point clear and to validate the claim,Yahushua quoted the Prophet Isaiah:
“The attitude of Yahweh (The Lord) is upon me. For which sake he anointed me: to announce the Wellness Message to the poor, he has sent me to heal the broken-hearted, to proclaim pardon to the captives, recovery of Insight to the blind, and to unstress the traumatized.”
That statement is the “stuff” of The Christ, the definition of the Christ in effect. It is proper to say that Yahushua is the Christ,but improper and false to state that the Christ is Yahushua. Backwards. In the same manner that Nero was the beast but the beast wasn’t Nero. The beast was a collective entity embodied by a foul government complete with a foul stench, according to John the Apostle.
So, John the Apostle understands the aforementioned explanation, modern people do not. Modern people are inclined to embrace Yahushua (Jesus) as the Christ, but when asked what is the Christ; the response is always, “the anointed one”, which is partially the case and begs the question anointed for what? To die?
Anointed for the purpose that both Isaiah and Yahushua stated. The fulfillment of that statement represents the essence of the Christ.
The addition of “the Christ” to the text of John’s letter “The Revelation” makes good sense for a couple of good reasons with professional courtesy in mind.
When one has spent enough time with the Greek text and its authors, one begins to sense attitudes and tones of the writers. The addition of the phrase “the Christ” is exceptional and helpful to the reader by adding perspective. Merely saying what was intended but left unsaid. The addition of the phrase “the Christ” is simply “skillful”.
That addition to the text has a positive and enlightening impact on the text which is helpful by bolstering the “spirit” of the text. The spirit or attitude of the text is made clear at the outset; that John depicts “The Way It’s Going to Be” and spells out “The Revelation of Yahushua “The Christ”, and proceeds to dramatize the theme from Isaiah which same theme articulates the essence of the Christ, making the addition to the text more helpful than harmful.
Just My Two Cents