From what I understand, "serious exploration of Classic Maya sites began in the 1830s. By the early to mid-20th century, a small portion of their system of hieroglyph writing had been deciphered, and more about their history and culture became known. Most of what historians know about the Maya comes from what remains of their architecture and art, including stone carvings and inscriptions on their buildings and monuments."
Mayan Civilization: Calendar, Pyramids & Ruins- HISTORY - HISTORY
The history that Moses and others had written down have been around for thousands of years, transmitted carefully and preserved. We can read the history of the kings and their good and bad points.