Did the great prophets believe in the Trinity, that God is three in one? And where is the evidence?

We believe in one God, and this is what all the prophets of God believed in, as is stated in the Holy Bible: (Deuteronomy 6:4-5) “Hear, O Israel: The Lord our God, the Lord is one! You shall love the Lord your God with all your heart, with all your soul, and with all your strength.” This one God, “after He spoke long ago to the fathers in the prophets in many portions and in many ways, in these last days has spoken to us in His Son, whom He appointed heir of all things, through whom also He made the world.” (Hebrews 1:1-2) Therefore, after the era of the prophets ended, God spoke to people through His Son, “God manifested in the flesh.” Note what Solomon says in Proverbs 30:2-4: “Surely I am more stupid than any man, and do not have the understanding of a man. I neither learned wisdom nor have knowledge of the Holy One. Who has ascended into heaven, or descended? Who has gathered the wind in His fists? Who has bound the waters in a garment? Who has established all the ends of the earth? What is His name, and what is His Son’s name, if you know?” Clearly, the text speaks of Almighty God. Now compare that with what is stated in Exodus 3:13-14: “Then Moses said to God, ‘Indeed, when I come to the children of Israel and say to them, “The God of your fathers has sent me to you,” and they say to me, “What is His name?” what shall I say to them?’ And God said to Moses, ‘I AM WHO I AM.’ And He said, ‘Thus you shall say to the children of Israel, “I AM has sent me to you.”‘” Now, do you realize the identity of the person spoken about in these texts? I know you will say no. Therefore, I want you to compare what has been said with what is found in John 3:13: “No one has ascended to heaven but He who came down from heaven, that is, the Son of Man who is in heaven.” How could the prophets give us what they had not seen? Do you know how? Through prophecy about the Messiah. This prophecy was mentioned by all the prophets of God, who depicted His image, His nature, His righteousness, His piety, the place of His birth, His death, and His suffering for our sake. They recorded all this so that the New Testament was written within the Old Testament. But the veil was not lifted until the symbols became realities. The Son, the Word, was born, lived among us, and we saw and knew Him. Then He died, rose, and ascended. Finally, after the Son ascended to heaven, He sent us His Holy Spirit. “Nevertheless I tell you the truth. It is to your advantage that I go away; for if I do not go away, the Helper will not come to you; but if I depart, I will send Him to you.” (John 16:7) This is what happened simply. This is called the progression of revelation. God is still one, but He appeared to us in human form in a specific period to accomplish a mission, which is to save all humans. After that, He sent His Holy Spirit to dwell in those who believe in Him. The prophet Jeremiah spoke of this, saying, “Says the Lord: I will put My law in their minds, and write it on their hearts; and I will be their God, and they shall be My people.” (Jeremiah 31:33) Also, the prophet Joel hints at this saying, “And it shall come to pass afterward that I will pour out My Spirit on all flesh; your sons and your daughters shall prophesy, your old men shall dream dreams, your young men shall see visions.” (Joel 2:28)