They might not both be after the Magnificence specifically, but they clearly each want to crush Cybertronians into a defeated slave race and a thing that literally knows everything is a hell of a means. As would being able to build new Cybertronian slaves that can turn into a million things and self-repair. I mean, the Magnificence might not be a magic resurrection machine, but it would know how to build one. Killing off blacksmiths is a means to an end--they are not needed any longer but they still have info. Opsec.