Immediately subsequent to this Jesus arrives from Galilee for baptism, and it seems to follow that John makes a prophecy about a great man arriving, and in the next verse, Jesus arrives! Yet, John found himself fit to dip Jesus into the Jordan – perhaps even holding him under water for a bit, which is significantly more daring than simply fixing his sandals – so Jesus was pointedly not the great man John had predicted.
But then John follows this up with a specific prediction about what the great man would do.