The implied information is that they became friends because Herod appreciated Pilate allowing him to judge Jesus. Alternate translation: "Herod and Pilate became friends with each other that very day because Pilate had sent Jesus to Herod for judgment" (See: [[rc://en/ta/man/jit/figs-explicit]])
This information is enclosed in parentheses to show that it is background information. Use a format that your audience would understand. (See: [[rc://en/ta/man/jit/writing-background]])