Jesus never explained one God/three persons. His disciples, initially Jewish, would have needed an explanation of the trinity. Most importantly Jesus told the woman at the well, " You worship what you do not know; we know what we worship, for salvation is of the Jews." John 4:24
Jesus was telling her that the Jews had a correct understanding of who God is...one divine person who defined himself with singular personal pronouns: I, Me, Myself.
One more verse, "All things have been delivered to Me by My Father, and no one knows the Son except the Father. Nor does anyone know the Father except the Son, and the one to whom the Son wills to reveal Him." Matthew 11:27
If Jesus revealed the trinity to his disciples, why didn't his disciples teach it since the trinity is a huge departure from what the Jews believed about God? Surely they would want to correct their Jewish brethren and let them know the "truth" about God.