In Adele Reinhartz's Caiaphas the High Priest she explains in Chapter 1 ("Caiaphas in Context") how little we know about Caiaphas outside of his depiction in the canonical Gospels. As regards our other surviving sources, he is mentioned only a few times in the writings of Josephus and possibly on an ossuary of a member of his family. I'm not surprised by this, per se, but I may have overestimated his importance outside of the self-understanding of incipient Christianity. In the final summarizing paragraph of the aforementioned chapter Reinhartz writes,
Robert L. Webb says something very similar about John the Baptist in John the Baptizer and Prophet: A Socio-historical Study wherein he writes,
John the Baptist was important in his own right, very important, but the Gospels minimize him making him important only in respect to Jesus of Nazareth. Yet, as Webb notes, if it weren't for the Evangelists' desire to make Jesus greater than John (an argument that apparently had to be made for some time after both John and Jesus had disappeared from the scene) there would be hardly any greatness of John left for us to ponder. Similarly, yet different, Caiaphas may have been just another High Priest mentioned by Josephus with a little more attention given to him that to the Baptist, but not a whole lot more. The Baptist has become a Saint; Caiaphas has been demonized. In this sense, Caiaphas doesn't get a fair shake in his remembrance and depiction, but he does gain notoriety that he may not have received if it weren't for his connection to Jesus' death.
One figure at the beginning of Jesus' life, the other at the end, both important in their own right in their own time, but not forgotten only because of Jesus.