We know how Islam started, we know how Christianity started, etc., etc. They began with a visionary prophet who gathered a small following, became popular because of his charisma or message, and eventually gained political power and influence that helped him or his followers spread the word.
Of course, those who became followers of the prophet accepted his lofty demands. They accepted those demands because of their faithfulness to the prophet and belief in his message.
Now to my point about Judaism. Judaism uses the national experience of events as the basis for its demands. No prophet requests their faith. No charismatic leader wins their allegiance. They are reminded, time and time again, to observe the Torah because of what they underwent in Egypt and committed to at Sinai. My argument is that these demands could only have been put forth on this basis if the people were aware of these events and their purported significance.
It's not exactly a proof of anything, but it's better written than Gosselieb. And also, I must apologize publicly for not showing Rabbi Maroof sufficient respect in my previous post. I didn't realize he is a Rabbi of a large shul (not that that's much of an excuse).