Jews understood, and still understand, what they are teaching. That is a very odd statement to say they do not. They understand very well the prophecies of a Messiah. They did not (and do not) believe Jesus is the Messiah.
Rebecca,
Hi and good day to you. One of Jesus’ teachings to the Jews was that He fulfilled the prophecies they were familiar with about the coming of their Messiah. Here are two examples:
John 8:53 Art thou greater than our father Abraham, which is dead? and the prophets are dead: whom makest thou thyself?
54 Jesus answered, If I honour myself, my honour is nothing: it is my Father that honoureth me; of whom ye say, that he is your God:
55 Yet ye have not known him; but I know him: and if I should say, I know him not, I shall be a liar like unto you: but I know him, and keep his saying.
56 Your father Abraham rejoiced to see my day: and he saw it, and was glad.
57 Then said the Jews unto him, Thou art not yet fifty years old, and hast thou seen Abraham?
58 Jesus said unto them, Verily, verily, I say unto you, Before Abraham was, I am.
59 Then took they up stones to cast at him: but Jesus hid himself, and went out of the temple, going through the midst of them, and so passed by.
Luke 4:16 And he came to Nazareth, where he had been brought up: and, as his custom was, he went into the synagogue on the sabbath day, and stood up for to read.
17 And there was delivered unto him the book of the prophet Esaias. And when he had opened the book, he found the place where it was written,
18 The Spirit of the Lord is upon me, because he hath anointed me to preach the gospel to the poor; he hath sent me to heal the brokenhearted, to preach deliverance to the captives, and recovering of sight to the blind, to set at liberty them that are bruised,
19 To preach the acceptable year of the Lord.
20 And he closed the book, and he gave it again to the minister, and sat down. And the eyes of all them that were in the synagogue were fastened on him.
21 And he began to say unto them, This day is this scripture fulfilled in your ears.
If they had understood the “prophecies of a Messiah” they would have recognized that He was the fulfillment of those prophecies. Some did, but most did not.