After Jesus rose from the dead there was a lot of hostility from people about Jesus and they tried to reduce Him to being just a man or just a good guy. The author of Hebrews saw all this conflict and knew that it needed to be cleared up. He showed what the Old Testament said about the Saviour and how He couldn't just be a good man, He had to be so much more.
Hebrews 1-3
The Old Testament doesn't allow Jesus to be anything but the complete solution.
