That prophet

John the Baptist was the Elijah (Matt. 11:14, 17:10-13) yet he said "i am not" (Jn. 1:21). He doesn't know that he was Elijah. Later he was also puzzled about Christ. Luke 7:9.

Now if John the Baptist doesn't know about himself, then how can he know who was Jesus? They asked him "are you the Christ?" He said "no". Then  they also asked,  "are you that prophet?" (referring to the prophet that Moses spoke about.  Deut.  18:15-18) He said "no".  For them both Christ and "that prophet" are two different persons. Their ignorance made them kill Jesus. They asked about it a person who doesn't know about himself yet.

Before the baptism of Christ John the Baptist knew Jesus very well but as a relative. (Luke 1:36). He knows the character of Christ that is why when he saw him he said, “I need to be baptized by you, and do you come to me?” (Matt. 3:14). After the baptism when the Holy Spirit came upon Jesus, then he realized that his relative Jesus is the Son of God. Let's hear it from his own words, "And I myself did not know him, but the one who sent me to baptize with water told me, ‘The man on whom you see the Spirit come down and remain is the one who will baptize with the Holy Spirit.’ I have seen and I testify that this is God’s Chosen One.” John 1:33‭-‬34.

Later before his death John was puzzled about Christ and asked “Are you the one who is to come, or should we expect someone else?” Luke 7:18‭-‬19.

You may be in the same position and puzzled about Jesus. Even Mary who heard Gabriel was stumbled, disciples who have been with him and heard the Father in heaven saying "listen to him" (Deut. 18:15-18) have stumbled, now John the Baptist who heard the heavenly Father and testified him have stumbled. To you i want to tell this. Do not look for some other prophet. He is "that prophet" (Act. 3:22). Listen to him (Mark 9:7).

"Blessed is anyone who does not stumble on account of me.” Luke 7:‬23.