‘And when they saw it, they made known concerning the saying which was spoken to them about this child, and all who heard it wondered at the things which were spoken to them by the shepherds.'
And once they had seen what they saw they went away and continually told everywhere what the angels had told them about this child, and there was great wonder everywhere as people considered what the shepherds said. They would make it known for years. It was a never to be forgotten event. Such amazement is another theme of Luke's writings (Luke 2:33; Luke 2:47; Luke 4:22; Luke 8:25; Luke 9:43; Luke 11:14; Luke 11:38; Luke 20:26; Luke 24:12; Luke 24:41; Acts 2:7; Acts 2:12; Acts 3:10; Acts 9:21; Acts 13:12). For the Good News is truly amazing.
Compare here Luke 1:65-66. These are the first two instances of what will become common in Luke's writings, especially in Acts, the ‘spreading of the word'. The news was so wonderful that it could not be held back.