When King Wu died within a few years of the conquest of Shang, his heir was a child and the new state was held together by nothing but the victory. The Duke of Zhou, Wu's brother, took the regency, faced a rebellion led by his own brothers in alliance with the surviving Shang royal house, campaigned in the east until it was broken, and then, on the tradition's account, handed authority back to King Cheng when he came of age instead of keeping it.
The religious consequence is the argument he is credited with making. The speeches preserved in the Book of Documents defend the conquest by saying that Heaven grants the right to rule on the basis of conduct and withdraws it for misrule, that Shang had held that mandate and forfeited it, and that Zhou now holds it on exactly the same terms. This is a remarkable thing for a victor to say, because it makes his own dynasty conditional and supplies in advance the argument by which it can be replaced. It became the standard justification for every later change of dynasty in China, and also the standard ground of criticism available to a minister, since a mandate that can be lost implies conduct that loses it.
One episode shows how closely the political and the ritual were bound together. The Metal Bound Coffer chapter of the Book of Documents records him praying to the royal ancestors during King Wu's illness and offering his own life in his brother's place, then sealing the prayer away in a box, where it lay until it was found years later and read as clearing him of ever having wanted the throne for himself.