Why is the most infamous act of Slaughter of the Innocents by Herod the Great appeared only in the Gospel of Matthews and not in the other Gospels?

Answer 1

Because it never happened.

It must be clearly understood that there is no particular requirement for anything at all to be recorded in the Gospels. Some events are recorded in all four some in three some in two and a few in only one. This is just one of them. It's no big deal, nor is it at all justified or logical. John makes clear that not everything could be recorded.

Herod was a butcher. Only a few children would have been killed in such a small town - a tragic thing but nothing for Herod. So, it is not surprising we have only one record of it.

If this event really happen, surely most of the contemporary writers of that time will write about this massacre; none did. In most probability, Matthew invented this myth to sensationalize his book.

As stated previously Herod was a butcher. On his death bed he gave orders for a group of his own people to be slaughtered by his soldiers after his death. This would prevent, so he thought, anyone celebrating his death (perhaps he got the idea he was not popular with his own people). However, his soldiers set the men free, as Herod was no longer around to enforce his murderous orders after he died and the people could celebrate both Herod's death and the release of the prisoners.

Thus, it is clear that Herod, though a great builder, was also a 'builder of tombs' and a murderous tyrant. Strange as it may seem in a small little known town the killing of a few babies, terrible as it was, was not likely to be given much notice in those days. Such things are not unknown in our own day when minority groups, such as Christians in various places are killed and no-one pays attention. This is happening on a daily basis.