As for the reasons the Classic Maya civilization disappeared. we have the story from Jared Diamond and others that it was due to ecological overshoot, famine, war, decadence of the ruling elite, etc. All of that may be true - it also may be that we are imposing our models onto a culture that was different in intention from ours. Other authors have noted that the individual city-states of the Maya were spread over a large area, and while some may have collapsed due to environmental pressures, it is odd that all of them disappeared so quickly. Also the Maya were apparently very skilled at low-impact agriculture - so skilled that as archaeologists have rediscovered their techniques, contemporary farmers are reviving them.
I am not an archaeologist, and admit that I don't know the answer. However, I do think it is interesting to at least consider Jose Arguelles' ideas from The Mayan Factor. He proposes that the Classic Maya, with their profound attunement to cycles of time, might not have expected to stay around forever: That the purpose of their civilization was to codify a system of knowledge and leave it behind so it could be rediscovered in the nick of time, as we approached the end of the cycle and the necessary transmutation of our species' consciousness.
I am also intrigued by Arguelles' notion that it is fascinating the Maya are called "maya" - when we consider that in Eastern philosophy, this term means the magical and creative power of the Gods in maintaining the illusion of the physical universe.