Why could Jesus not be the object of faith for the Gentile world before his death and resurrection?
The Gentile world could not yet look to Jesus in faith because He had not yet experienced death, burial, and resurrection. He first had to fulfill the type pictured by Jonah, who was not a fit servant until the fish released him, prefiguring resurrection, and only then did he go to Gentiles.
Les explains that Jonah's three days and three nights in the fish were a type of Jesus' death, burial, and resurrection. Jonah could not go to the Gentiles until after this type was fulfilled; only after being pitched back on shore, a picture of resurrection, did he go to Nineveh, and they repented. Likewise, Jesus says that until He had experienced death, burial, and resurrection, He could not be the object of faith for the mass of the Gentile world. After that finished work, Gentiles who were far off are made nigh by the blood of Christ, not by the Law or the covenants.