The reason that Nobuhide was forgiven and allowed to return to the service of his master soon after the death of Nobumori is that Nobunaga decided that he had fully reflected on his conduct or that, from another perspective, Nobunaga was aware that his previous evaluation was wrong.
信盛の死後まもなく信栄の帰参が許されたのは信長が反省したと判断した、もしくは自身の評価の誤りを自覚してたからとも解釈できる。