Angels knew words spoken by God long before humans so they knew very early of the Christ coming. They knew before any prophets knew. They knew there would be a Christ. The words God spoke to them in some ways revealed it to them. Some knew it better than others. This is even before the time of Noah or his predecessors. Just like we can discuss the Christ today, so they could discuss him even before 3000 BC. We cannot say the same about other people. “Before Abraham was born, I am” said Jesus.
