When John the Baptiser, who had been locked up in the prison at Macherus, heard about everything that Jesus was doing he called for two of his disciples and sent them to Jesus to ask if he really was the Messiah?
When the men found Jesus, they said to him, “John has sent us to ask you: ‘Are you really the Messiah we have been expecting, or should we keep looking for someone else?’” TJB 10:34-35
Even John the Baptist hadn’t expected this turn of events. Wasn’t the Messiah meant to be raising an army to overthrow the Romans and come and rescue him? Instead of hearing about rumours of uprisings John who was in prison in the fortress at Macherus hears that Jesus is hiding in the wilderness, having parties with tax collectors, choosing questionable disciples from among the common people etc. John’s faith in the Messiah was faltering.
John’s question about there being another Messiah is not only rooted in his lack of faith but also in the teachings about the two Messiahs. Rabbis over the centuries struggled to piece together the scriptures concerning the Messiah as they seemingly conflicted with one another. How could a conquering King who lives forever die a humiliating death? Hence they came up with the theory that there must be two Messiahs.
There are many scriptures that talk about the eternal king. Here is one from Daniel 7:
“In my vision at night I looked, and there before me was one like a son of man, coming with the clouds of heaven. He approached the Ancient of Days and was led into his presence. He was given authority, glory and sovereign power; all nations and peoples of every language worshiped him. His dominion is an everlasting dominion that will not pass away, and his kingdom is one that will never be destroyed. Daniel 7:13-14
Then just 2 chapters later Daniel writes this:
After the sixty-two ‘sevens,’ the Anointed One will be put to death and will have nothing. Daniel 9:26
What the Jews couldn’t see was the resurrection of the Messiah and 2000 year gap between the resurrection and the coming of the Messianic king.