User blog comment:Baptain/Second Fruit Theory/@comment-29561365-20160810143116/@comment-71.3.124.143-20160814032721

It's because he ate the Dark Dark Fruit, or the Yami Yami no Mi, that he was able to absorb Whitebeard's devil fruit himself. One of the powers of the fruit is to absorb object or energy around the user so maybe he used a hidden power of the Yami Yami no Mi to transfer or "absorb" other devil fruits. Maybe this is why he sought after the fruit so much while he was a part of Whitebeard's crew and killed one of the crewmates, who had found it, to obtain the Yami Yami no Mi.