Why would Elon Musk pivot from Mars to the Moon all of a sudden?

Elon Musk's SpaceX has shifted its focus from colonizing Mars to building a self-growing city on the Moon, citing a more achievable timeline of less than 10 years. This pivot comes as Blue Origin advances its lunar exploration, potentially threatening SpaceX's lead. Musk's increasing interest in artificial intelligence and space exploration's role in it further drives this decision. The Moon's resources and strategic advantages, including its potential as a high ground, also play a part in this strategic shift.