Me and my brother discussed this a while back. This is the deduction we got from our discussion:
Onewa always said Vakama was cross-wired, and believed he got his visions from looking into the fire for too long. Now, many of this look as if this is just a joke. But perhaps he is right!
Now, if we look at MNOG and other BIONICLE media from 2001-2003, Vakama always knew the prophecy. We could see in MNOG that he always seemed to face the fire for some strange reason, and afterwards, he knew exactly what was going to happen next. He seemed to know prophecy the other Turaga always knew, and we deducted that this was because of his so-called visions.
But what was the origins of these visions? Did he have something wrong with his mind, which allowed him to see destinies while others did not? Perhaps.
You see, Vakama was a forger, it was his Matoran job. But soon after Lhikan's disappearance, Vakama began to have visions. We started to deduct that perhaps Vakama, being near the fire much longer than other Matoran, may have had some things going on with his brain. We don't know what makes it like that, all we know is that fire helps him look into the future.
Although, a few ideas came to mind:
1. While trying to make the Mask of Time, all the fails had a little bit of the power, which affected his mind so he could see into the future by visions.
2. The Great Beings made him so he had a, literally, cross-wired mind, so he could see the destinies of others.
3. Members of the Order of Mata Nui have been known to come into visions, like Krakau, and perhaps Lhikan was a secret member of the Order, giving the leader of the new Toa Metru guidance to defeat Makuta and his plot. In the process, looking into the fire triggered something in Vakama's mind, which gives him visions so that he can see the future and other destinies.
In the story, the origins of Vakama's visions are unexplained. Greg has not even given an answer to why his visions happen.
So, this topic was made. Discuss your ideas on why Vakama gets his visions! Do you agree with my ideas? Or do you have different ideas! Reply!