Is it very explained what Dark Gaia's motives were?

Why did he create Crysta and take on the form of an old man and acted as its Elder? And why did he make Ark resurrect the world above and trick him into reviving a mad scientist? And why did he make the other villagers turn into spirits to attack Ark on his return? Was the last part purely spiteful (given his taunts Ark about the consequence of learning too much and there really wasn't any real reason to make the villagers attack Ark). And what was his original motive for the events of the game? Was he greedy for something or did he have some deeper motive or was he just evil for the sake of it?