Mayan high civilization was advanced in astronomy projecting events by more than a quarter million years into the past and future. Math and literature has less evidence since most of it has been destroyed.
WHAT HAPPENED TO THEM?
They descended into madness and society collapsed en masse.

Here is the explanation; They had a magnificent water purification and storage technology. In their city plazas they created an expansive water collection area that filtered through fine sand and minerals to purify the water and directed it to underground storage and irrigation complexes. All well and good but the decorative buildings and temples were painted a bright vermillion red that was full of mercury. Over time the entire filtration layers became polluted with mercury that flowed off the pyramids and structures. Mad as a hatter is the English expression for those who made hats with mercury. China had its tradgedies with mercury and so did the Mayans. In Rome their pollution was lead.
The transition to madness from a poison water supply may have been a remarkable story that probably took longer to take hold than we might expect.