The Green Baby was DIO's reincarnation. The reason for this is that the 14 phrases that DIO needed to remember were things spoken to him from before. I believe they were a part of his lulliby or something? IDK. But they represent things that he dd in his life, and they were carved into his stand/soul so he would never forget. Then, when Pucci spoke the 14 phrases to The Green Baby, the Green Baby became violent and fused with him (Such a DIO move) and formed the stand C-Moon (Which had time manipulation abilities which Pucci couldn't activate, but would activate on their own (Signifying that DIO was conscious within the stand which bore a resemblance between White Snake and Green Baby.)
Here is the excerpt of the stair way to heaven in DIO's diary.
"What you need is my Stand "The World".
What you can find beyond the powers of my Stand is where you need to go in order to find Heaven.
What you need is a trustworthy friend. He must be someone capable of controlling his own desires. He must be someone who is not interested in political power, fame, wealth, or sexual desire, and who chooses the will of God before the law of humans.
Will I, DIO, be able to meet someone like this one day?
What I also need is the lives of more than 36 humans who have sinned, because those who have sinned harbor a strong power within.
There are 14 phrases that one must keep in mind:
Spiral staircase (らせん階段 Rasen Kaidan)
Rhinoceros beetle (カブト虫 Kabutomushi)
Desolation Row (廃墟の街 Haikyo no machi)
Fig tart (イチジクのタルト Ichijiku no taruto)
Rhinoceros beetle (カブト虫 Kabutomushi)
Via Dolorosa (ドロローサへの道 Dororōsa e no michi)
Rhinoceros beetle (カブト虫 Kabutomushi)
Singularity point (特異点 Tokuiten)
Giotto (ジョット Jotto)
Angel (天使エンジェル Enjeru)
Hydrangea (紫陽花 Ajisai)
Rhinoceros beetle (カブト虫 Kabutomushi)
Singularity point (特異点 Tokuiten)
Secret emperor (秘密の皇帝 Himitsu no Kōtei)
I'll engrave these words onto my Stand so I won't forget them. What is most necessary is "courage"; I must have the courage to destroy my Stand momentarily.
As it disintegrates, my Stand will absorb the souls of the 36 sinners and will give birth to something utterly new.
Whatever is born will "awaken". It will show interest in the 14 words that my trusted friend will utter... My friend will trust me and I will become his "friend".
Lastly, I need an appropriate location. North latitude, 28 degrees, 24 minutes, West longitude 80 degrees, 36 minutes...
Go there and wait for the New Moon...
That's when Heaven will come."
The Fourteen phrases are things from DIO's life.
The Spiral Staircase. The place where his story began. The Joestar Mansion.
Rhinoceros Beetle. It to me resembles the arrow that grants stands and the one that made Giorno's Gold Experience Evlove. We know that this arrow is the one DIO had, because it was the only one Polnareff took from Egypt. And the Bow and Arrow was spotted in the back of DIO's mansion.
Desolation Row is Dio trying to kill George Joestar, and his eventual fall from grace.
Fig Tart. Could that be when Erina brought fruit to Jonathan? And Dio became envious?
Via Dolorosa. This was the path of sorrow that that Jesus walked in Jerusalem. It could also signify Dio trying to make Jonathan's life sorrowful.
Rhinoceros Beetle. (Not quite sure what this one means)
Singularity Point. This references things coming together. It might reference things coming to a head with Jonathan, where Jonathan discovered Dio's plot.
Giotto. This man was a painter. His most promenent painting is of the The life of the Virgin Mary and The Life of Christ. This could reference him becoming something new. A rebirth as something more than human.
Angel. This obviously means the statue of an angel that stabbed Dio in the burning mansion.
Hydrangea. It is a word derived from Greek and means ‘water vessel’. Possible reference to the ship and/or his coffin where he and Jonathan became one person.
Rhinoceros Beetle. I do not know this one either. It is possible that they are used to refer to the Joestars.
Singularity Point. This is things coming to a head again and may mean DIO's defeat at the hands of Jotaro.
Secret Emperor. This is reference to not something he has done, but will do. Pucci will achieve heaven and become a King, and DIO will become the Secret Emperor, which also signifies that he is living on through Pucci as a part of his soul, or maybe even as the stand Made in Heaven.
By the sounds of the Diary, DIO was ALWAYS supposed to die and be reborn as the Green Baby. "What is most necessary is "courage"; I must have the courage to destroy my Stand momentarily." As we all know, destroying your stand equals death since it is your soul. But he said as it is destroyed, it will absorb the souls of the 36 and give birth to something new.
As it disintegrates, my Stand will absorb the souls of the 36 sinners and will give birth to something utterly new. Whatever is born will "awaken". It will show interest in the 14 words that my trusted friend will utter... My friend will trust me and I will become his "friend" Here, the wording is precarious. DIO at first speaks of the Green Baby in third person, as if it's someone else. But after it hears the words that his friend would utter, DIO refers to HIMSELF. He says that his friend would trust him and he would become his "Friend". The quotes signify that he doesn't mean a literal friend, but something similar. Perhaps he means "Stand" since Kakyoin's stand was considered his imaginary friend in his early years. And this keeps with the idea that the Green Baby merged with the stand. This means that The Green Baby is DIO. DIO is C-Moon, and C-Moon evolves into Made in Heaven. Thus, DIO is reincarnated as Made in Heaven. And yes, it would be even better if Jonathan really was Star Platinum. Jonathan versus Dio all over again, and just as Dio said before "You can never beat me, JoJo!"
Also, they both have worn feathers around their necks.
...That's enough for me!