Why did Elon Musk create Optimus?

Could you please elaborate on the motivations behind Elon Musk's creation of Optimus? It seems like an ambitious and innovative project, so I'm curious to understand what inspired him to embark on such a journey. Is it a way to further advance the field of robotics and artificial intelligence, or is there a more specific goal or vision that he has in mind? Additionally, how does Optimus fit into Musk's broader portfolio of companies and projects, and what role does he envision it playing in the future of technology and society?