You ought to be baffled because you have reality exactly upside down in the manner in which you weight the evidence.
First, it is the Divine that has communicated with man by various means, which includes Revelation. In Judaism, this began with God speaking to Abraham. Centuries followed in which Yahweh continued to reveal to the Jews that which He wanted them to know about Himself and His plan. The Bible includes accounts of Yahweh’s interaction with the Jews, i.e. speaking through various prophets. The Divine plan included the Incarnation of the Savior.
There are also extra-biblical accounts of the Savior, which were written by non-Christians, such as is contained in the works of the Jewish historian Josephus. Those familiar with ancient history will know well of the independent Roman accounts.
In the ancient Greek world, philosophers, by means of reasoned arguments, demonstrated the existence of the immortal human soul, and the existence of God. For example, Aristotle demonstrates the existence of God as the Prime Mover or Un-caused Cause…
In sum, there are literally millenniums worth of evidence which you must summarily and dogmatically discount in order to justify atheism. And I have only touched lightly on a small part of the evidence. The Judeo-Christian tradition is built on a solid edifice of evidence that has not been dis-proven, only denied or ignored. So, I doubt that you will come up with any argument against it that is worth debating.
On the other hand, What argument(s) can you advance to disprove the traditional philosophical demonstrations for the existence of God?
Give it your best shot, ace!