This view states that the Father, the Son, and the Holy Spirit never all exist at the same time--only one after another. (CARM)
Could be true because:
John 14:
15“If you love me, keep my commands.
16And I will ask the Father, and he will give you another comforter to help you and be with you forever—
17the Spirit of truth. The world cannot accept him, because it neither sees him nor knows him. But you know him, for he lives with you and will be
c in you.
18I will not leave you comfortless; I will come to you.
19Before long, the world will not see me anymore, but you will see me. Because I live, you also will live.
John 16:
7 But very truly I tell you, it is for your good that I am going away. Unless I go away, the comforter will not come to you; but if I go, I will send him to you.
1. The advocate was already there with them
2. Jesus had to go for the advocate to come into them, if Jesus doesn't go, the advocate doesn't come
3. Jesus does not leave them comfortless, he comes back to them shortly
Conclusion
This simply is not the way two distinct persons work, that one has to go for the other to come and if he doesn't go, the other won't come. Jesus is claiming to be the Holy spirit here. He must go and come to them in another form.
Jesus, Father, and the Holy Spirit were manifest on the occasion of Christ's baptism. Further, God's manifestation on earth is confirmed for example in 1 Timothy.
And without controversy great is the mystery of godliness: God was manifested in the flesh, justified in the Spirit, seen by angels, preached among nations, believed on in the world, and received up into glory. (1Ti 3:16)
The baptism of Jesus refutes trinity. Jesus as He stood in the water getting baptized was already one person, one mind and one God by Himself- so the idea that God must be 3 persons in one is already in tatters not unless you change and say that Jesus was not fully God until the Father spoke and the holy spirit descended, then it means we can split God into 3 parts (God forbid).
Whatever happened at baptism is written for your understanding and not for confusion and you must also know that only John the baptist and Jesus saw the dove and heard the voice, meaning that everything was happening in the spirit.