I believe in science, NOT conspiracy theories. Would anyone really be all over this if it hadn't been drilled into their heads via psychotic-inducing movies? News media blowing things out of proportion (they're quite good at that)? No.
No one would know, no one would care, and frankly...anyone who thinks they knew what an ancient civilization was thinking/doing all the time is insane. And basing the rest of their lives off that? Pointless.
We don't know what they were thinking. Why they stopped. What we DO know is that so many "prophecies" have failed. Over and over. What makes this so different?
Yeah, ice caps are melting. Not the first time in Earth's history. Yeah, global warming sucks. Not the first time in Earth's history. If something happens, it'll happen because of science and the mercy of nature. Not because an ancient civilization stopped a calendar (a calendar which, btw, we don't even know if we're accurately aligned with!)