How do you know they weren't in the original if we do not have the original because all the originals of all the Gospels have perished with use?
Why do you believe verses 9-20 do not match the surrounding text ?
Why do you think they do not match the rest of the Gospel accounts ?
One characteristic of 9-20 that conforms with the character of the rest of Mark is its focus on evangelism. Mark is the gospel that is represented by the face of the ox: animal that bears burdens, is offered in sacrifice and ploughs and brings in the harvest. Mark presents Christ as the suffering servant, and the sin-bearer, and the bringer of good news. He also presents Jesus primarily as the consummate evangelist.
The other gospels are represented primarily by other faces, and primarily highlight other aspects of Jesus, while nevertheless showing something of the other three faces.
Matthew: the face of a lion, the promised King and the consummate apostle,
Mark: the face of an ox, the promised suffering servant and atonement sacrifice, and the consummate evangelist.
Luke, the face of a man, the promised seed of the woman, the kinsman redeemer, and the consummate pastor-teacher
John: the face of an eagle, the promised prophet like unto Moses, and the consummate prophet.
If we look at the opening verses of Mark "1 The beginning of the gospel of Jesus Christ, the Son of God."
Now we look at the ending -
16 And when the sabbath was past, Mary Magdalene, and Mary the mother of James, and Salome, had bought sweet spices, that they might come and anoint him.
2 And very early in the morning the first day of the week, they came unto the sepulchre at the rising of the sun.
3 And they said among themselves, Who shall roll us away the stone from the door of the sepulchre?
4 And when they looked, they saw that the stone was rolled away: for it was very great.
5 And entering into the sepulchre, they saw a young man sitting on the right side, clothed in a long white garment; and they were affrighted.
6
And he saith unto them, Be not affrighted: Ye seek Jesus of Nazareth, which was crucified: he is risen; he is not here: behold the place where they laid him. (The angels evangelised the women and send them with the good news).
7
But go your way, tell his disciples and Peter that he goeth before you into Galilee: there shall ye see him, as he said unto you. (
the women are sent as evangelists to take good news to the disciples)
8 And they went out quickly, and fled from the sepulchre; for they trembled and were amazed: neither said they any thing to any man; for they were afraid. (The women, on their way the the disciples, were not convinced by the angels' testimony, so told no one they met until they arrived at the disciples lodgings.)
9 Now when Jesus was risen early the first day of the week,
he appeared first to Mary Magdalene, out of whom he had cast seven devils. (
Jesus evangelised Mary.)
10
And she went and told them that had been with him, as they mourned and wept. (
She believed she had seen Him risen and evangelised the disciples.)
11 And they, when they had heard that he was alive, and had been seen of her, believed not. (B
ut they did not believe her testimony of seeing Jesus risen.)
12 After that
He appeared in another form unto two of them, as they walked, and went into the country. (
Jesus evangelised two disciples.)
13
And they went and told it unto the residue: neither believed they them. (They
evangelised the eleven,
but they did not believe their testimony of seeing Jesus risen.)
14 Afterward he appeared unto the eleven as they sat at meat, and upbraided them with their unbelief and hardness of heart, because they believed not them which had seen him after he was risen. (Jesus
evangelised the eleven and
they believed they had seen the risen Saviour.)
15
And he said unto them, Go ye into all the world, and preach the gospel to every creature. (
Jesus sends them as evangelists to take the good news to the world.)
16 He that believeth and is baptized shall be saved; but he that believeth not shall be damned.
17 And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues;
18 They shall take up serpents; and if they drink any deadly thing, it shall not hurt them; they shall lay hands on the sick, and they shall recover. (Knowing that the testimony of men or angels was not enough to convince Jesus' own disciples, but they needed a personal experience of the risen Christ, Jesus promised to demonstrate His real risen presence through signs to confirm the message. )
19 So then after the Lord had spoken unto them, he was received up into heaven, and sat on the right hand of God.
20
And they went forth, and preached every where, the Lord working with them, and
confirming the word with signs following. Amen. (They went out and shared the good news, and Jesus was faithful to conform it with signs.
That this ending of Mark is so replete with allusions to evangelism, inc=dicates to me that it is one spirit with the focus of the rest of Mark's gospel.
