Question
Why does the soul fall prey to maya, when it resides in the body?
Answer
You are not in the body, you are only apparently in the body. There is no need for the Lord to do anything, you are already free. You cannot become something which you are not. If you were not already free, you could never become free. The Asthvakra Samhita (1.11) says - "A man who considers himself free is free indeed, a man who considers himself bound remains bound. This popular saying is true - as one thinks so one becomes."
Questions such as why...? can only be asked in the relative universe. There are no questions, no why, from an Absolute standpoint.
From an advaitic standpoint, you only apparently exist in a body. This is called vivarta vada - apparent manifestation. The universe only apparently exists. Does the lake in a mirage wet the earth below? A cloud only apparently covers the Sun...can a cloud of a few hundred meters really cover something which is millions of miles in diameter?
Note: “The question: Why does the soul fall prey to maya, when it resides in the body?” is licensed by Stack Exchange Inc (https://hinduism.stackexchange.com/); user contributions licensed under CC BY-SA.