Though this account has the authority of “consensus” of the historians behind it...
Though this account has the authority of “consensus” of the historians behind it, its authenticity, nevertheless, is suspect on the grounds of “circumstantial evidence.” There are too many “coincidences” in it. No one questions the fact that it was Ibn Muljam who killed Ali. But was it his own idea to kill him? It is quite probable that the idea was planted in his mind by someone else who used subliminal techniques for doing so.
Ibn Muljam didn't know that he was only a cat's paw, and he went ahead and killed Ali. At this time no one in Dar-ul-Islam was more interested in the assassination of Ali than Muawiya. The plot to kill Ali, the skill displayed in its execution, and its success, show the touch of consummate subtlety and a high degree of professionalism which were characteristic of Muawiya alone, whereas Ibn Muljam was nothing more than a bumpkin.
Muawiya employed the same “skill” in removing from the scene, real or fancied threats to his own security and power, on numerous other occasions in later times, with the same results. Muawiya's spies had informed him that Ali was making preparations for the invasion of Syria. In the battle of Siffin, Muawiya had not responded to chivalrous treatment by Ali.
This time, therefore, Ali had decided, not to fight a lingering action but a swift one that would quell Muawiya's rebellion, and would restore peace to the embattled empire of the Muslims. Muawiya also knew that Ali had, this time, both the ability and the resolution, to bring the conflict to a speedy and successful conclusion. His only hope, therefore, for his safety in future, as in the past, lay in the succor that he could get from his old and trusted “allies” – treachery and intrigue.
He, therefore, mobilized them, and they didn't disappoint him. Muawiya made the act of the assassination of Ali look absolutely spontaneous and convincing by making himself and his crony, Amr bin Aas, the potential and intended “victims” of the conspiracy and fanaticism of the Kharji anarchists.
But both of them “escaped” assassination by a rare “stroke of good luck.” One of them “fell ill” on the day he was to be “assassinated,” and did not go into the mosque; the other did not fall ill, but went into the mosque wearing his armor under his cloak. He was “attacked” by his “assassin” but was “saved” by his armor.