The Gospel of Mark is thought to be the oldest of the four Gospels which have been accepted by the Church and, it seems, Protestant churches as well. As we know, there are other gospels which were unaccepted, if not purged, by the early Church and thus excluded from the canon. The reasons for their exclusion makes an interesting study.
The Gospel of Mark is interesting in itself though. In its original form, it didn't include what is included in other Gospels, particularly when it comes to appearances of Jesus after the Redemption. It also includes statements it states were made by Jesus regarding what's generally described as the Second Coming and the commencement of the Kingdom of God which are considered troubling to many Christians. Those statements are to the effect that it will occur during the lives of those to whom he spoke, or within a generation (e.g. Mark 9:1).
Early Roman critics of Christianity, such as Celsus, noted this and other peculiarities and inconsistencies in the Gospels. They also noted that at the time they wrote, those who heard Jesus speak these words and their generation had long since passed away, and the world continued on nonetheless just as it had for centuries. They reasonably inferred from this that Jesus must have been a false prophet if not something worse.
No less a zealous apologist for Christianity than C.S. Lewis felt that this is most "embarrassing" passage in the Bible. Earlier apologists were also well aware that the Gospel ascribed to Mark was a problem in various respects. Origen wrote a book to refute Celsus, though it's thought he didn't do a very good job.
Christians and Christianity have struggled over the long years to account for the Gospel of Mark. It was maintained at one time that this Gospel was a mere summary of the Gospel of Matthew, and less important. Naturally, it couldn't be maintained that the Gospel of Mark was wrong, or inaccurate in any sense, if it was thought to be the Word of God. But the fact that the available evidence indicates it was written before the other Gospels makes this explanation unhelpful.
And so rather than accepting that it's possible the words of the Gospel of Mark should be taken to mean what they clearly say, which would be to acknowledge that Jesus was wrong and so could not be God, those words have been the subject of interpretation. For example, it's been claimed that what Jesus spoke of according to Mark was something different from the real Second Coming, but a spiritual one resulting from his death on the cross or his Resurrection, or was somehow intended to refer to the destruction of the Jewish Temple by the Romans in 70 C.E.
The Romans certainly destroyed the Temple. I've now seen "with my own eyes" the Arch of Titus and the relief on it showing men of the legions marching in triumph holding the riches of the Temple. But it isn't clear to me why Jesus wouldn't simply have said that was what he was referring to, nor do I see how the Kingdom of God came to be established due to the sacking of Jerusalem.
Ancient writings, such as those of the obliging pet of the Flavian emperors, Josephus, tell us that the Roman world and especially Palestine were host to a number of men who worked miracles and taught that the end of the world was coming. Jesus thus was not unique in that respect. It appears such men are not unique in our history, as there have always been those who proclaim the end of the world is nigh for one reason or another. There are such men today, in fact, and like their successors they've found that they have admirers enough to keep them happy, and even wealthy though not wise.
I don't know enough of religions besides Christianity to say whether this ecstatic belief that the world will end and only certain of us will be saved is characteristic of religious belief everywhere, or limited to the various kinds of Christians. Christians, though, have too often believed someone to be a prophet and have anxiously awaited the end of others, but not themselves. Periodically they venture to some place or other, gathering at the appropriate time to witness the Second Coming, only to be disappointed. Their prophet generally explains thereafter that he was wrong in his count, or misinterpreted signs given, and comes up with another date which in turn is found not to be the day the world ends or Jesus comes again.
This isn't all that surprising. But what is surprising is that the people disappointed in their expectation of annihilation blithely accept explanations offered and believe that the end will come at whatever new date is selected by their erring leaders.
This kind of faith, if it may be so called, is difficult to explain. The faith in an apocalypse must be very stubborn to survive continuing disappointment and the relentless survival of the world and its sinning inhabitants. Mere stupidity can't provide the only explanation. The hope for an end of the world must be extreme.
The world is a difficult place to live, but it's probably now a less cruel place than it was for the poor and disaffected of the Roman Empire nearly 2,000 years ago. What is it in some of us that provokes such an enormous discontent, such a fervent dissatisfaction with the world and with other people, that we hope and pray that the world will be destroyed and most of us swept away by an angry god?t
The Gospel of Mark makes me wonder about how the early Church grew and Christianity became the state religion of the Roman Empire. As those who expected the Kingdom of God to commence while they were still alive noticed that it had not arrived, did they come to question whether Jesus was God? There are statements in Paul's letters which indicate he was aware of this possibility and spoke against it, even as he spoke against those followers of Christ who were too Jewish to accept that he was the (self-proclaimed) apostle appointed by God. Is the Christianity we know that of Paul and not that of Jesus? That isn't a new notion by any means.
Would Christianity have spread if Jesus was portrayed only as he is in the Gospel of Mark, in its original form? In other words, would it have come to dominate the Western World without the later Gospels, the Acts, and the writings and travels of Paul, who never knew him while he was alive? Or would it remain what pagans thought it was initially, a Jewish sect?
Regardless, we can see in this expectation of and hope for the end of the world, the thirst for martyrdom, and the reverence for the relics of saints which began very early, why educated Romans (like Marcus Aurelius) thought the Christians to be irrational and irresponsible, and even insane, and why the Emperor Julian and others thought Christianity to be a death cult.