Complex sentence: He also successfully wipes any memory of him or Earth from her mind, instead programming these and a letter from him to come to her later in life in hope that she would better understand the circumstance once she has matured.
Split into simpler sentences: He also successfully wipes any memory of him or Earth from her mind, instead programming these and a letter from him to come to her later in life. In hope that she would better understand the circumstance once she has matured.