Creatures in a world where only the strongest would survive were destined to clash. Order was only there to keep things together, but no one could destroy an order that wasn't meant to keep things together.
Legacy was one of the orders that weren't meant to keep things together. It was an occurrence that would devastate the order that everyone had grown accustomed to. As a result, when Xiulong received the legacy to create Lucas as a candidate for the new Divine Emperor, he followed each step.
He went back in time and caused a commotion before transporting Lucas to the Four Heavens via the Universal Bridge, which an ambassador should seal. He went to great lengths to keep himself entertained, which was his legacy's purpose for him.
He then left Lucas with the legacy of destroying the established order. He did not, however, anticipate everything going wrong. He should have done better, but he couldn't because his legacy was against the current Divine Emperor.