Saying that the Mayans "predicted" stuff is as accurate as Nostradamus doing the same thing. Translation of Mayan writings is going to be sketchy at best - they weren't exactly friendly to outsiders. So you start with a mistranslation (even if only slightly) and that gets taken over the years to mean different things by different people (before written documentation). The next thing you know an event has happened and then in hindsight you can apply some of that "knowledge" to the event and claim that they were prophetic.
If, for example, I said that a life-changing catastrophy will happen near the beginning of the 21st century it could mean anything. A plane might crash, a boat might sink. Something is inevitably going to happen that will change a few people's lives. It's called "subjective validation", people. You give vague information so that people who want to believe something read more into it than you could ever have known to begin with.