After all the despair and dashed hopes of the crucifixion, the narrative winds down to what seems to be a miserable ending. It turns out Jesus had some sympathizers on the Sanhedrin, but they kept their mouths shut out of fear. Now, after Jesus is dead (too little too late) he wants to treat the body of Jesus with respect by giving him a proper burial. Now at last they are taking an open stand (but if pressure comes to them, they can still just say they were trying to be decent Jews).
Their embalming of Jesus’ body shows us, among other things, that Jesus was truly and actually dead, and that there was no expectation of any kind of rising (resurrection). The man whom they thought might actually be the messiah was just another victim. A sad day indeed.
They buried him in a tomb very close to the execution site. John is building his case: Jesus was really dead, his followers had no expectation of resurrection, there were plenty of witnesses to the manner and place of burial, and no other body was in that tomb (just so there would be no confusion.
No one has a clue what is coming.