The four canonical gospels were written between 65 and 100 AD, so at a time when Christ was still in living memory and people who had met him were still alive.

They were written some decades later, but all within the century. It is probable that some intermediate texts existed in between as well which were used as references in writing some of the ones we have. It is in any case a very short game of telephone.

It should also be added that the Old Testament itself is compiled from many books and versions as well as oral traditions written down long after the fact. The New Testament is in this sense a much much simpler case than the Old Testament.

Now Jesus did indeed speak Aramaic, but there is nothing particularly special about Aramaic, it was just a major language in the region at the time. He spoke Aramaic for the same reason the Gospels are written in Greek, it's what the target audience best understood (Greek was the Lingua Franca across the Eastern mediterranean, and the Apostles had left to preach in places like Antioch and Alexandria).

The New Testament also includes the Letters of the Apostles. This is relevant because these are letters written by the Apostles while still alive, weighing on on theological questions which early Christian communities faced. Now it should be said that some of these letters are almost certainly ascribed to apostles after the fact, and so there is some scholarly debate about them, but the majority are accepted to be written by the Apostles themselves, and only a minority are debated or considered to be written by their successors.

At the very least, they certainly give us a very good idea of what the followers of Christ during his life and immediately following his death actually believed. It is thus very difficult to challenge the historical fact that early Christians who lived contemporaneously with Christ believed that he was the Son of God and had died and risen again. This does not mean that these supernatural things must be true, but it does mean that they are very likely what Jesus taught and what his followers believed.

For any alternative interpretations, one would have to start digging into non-canonical gospels (apocrypha) and most of them are written much later and not considered canonical gospels for a reason.

Getting back to the canonical Bible, it should also be said that it contains four gospels which are four independent texts by separate authors from the first century AD, all of which cover the life and teachings of Jesus Christ. They focus on different perspectives and may include different stories, but their overall message is the same. This should at the very least lend further credence to the fact that these teachings are not just the opinions of one guy, but widespread, agreed upon views among early Christians about who and what Christ was, how he lived and what he taught.

The consequence of this is that if Jesus was an authentic prophet with true teachings, he must also be the Son of God. For this not to be the case, it requires the conspiracy of all his Apostles crafting a false narrative about his godhood and resurrection, and no one breaking ranks or telling "the truth" from any of Jesus' followers who knew him in life. But if this were to be the case, then we have no reliable accounts of Jesus' teachings at all, so whatever he taught and no matter how authentic we cannot follow it because we do not know it.

If the story of the Son of God were to be a deliberate lie merely to gain popularity for his message, then it would at least seem likely that Jesus would been a part of and mastermind of this conspiracy, rather than a victim of it.