Glory be to Allāh! How staunchly you cling to innovated passions and painful bewilderment along with ignoring the facts and rejecting strong reasons which are liked by Allāh and serve as pleas for the people. As regards your prolonging the question of ‘Uthmān’s  murder the position is that you helped ‘Uthmān when it was really your own help while you forsook him when he was in need of help; and that is an end to the matter.
 There is no question of denying that Mu‘āwiyah claimed to help ‘Uthmān after he had been killed, although when he was surrounded and clamoured for his help by writing letter after letter Mu‘āwiyah never budged an inch. However, just to make a show he had sent a contingent towards Medina under Yazīd ibn Asad al-Qasrī, but had ordered it to remain in waiting in the valley of Dhū Khushub near Medina. Eventually, ‘Uthmān was murdered and he went back with his contingent.
No doubt Mu‘āwiyah wished ‘Uthmān to be killed so that he should create confusion in the name of his blood and through these disturbances clear the way for allegiance to himself (as Caliph). That is why he neither helped him when he was surrounded nor thought it necessary to trace the murderers of ‘Uthmān after securing power.