Complex sentence: The other reason for his political downfall was that Christmas Island, administered by Singapore at that time, was transferred to Australia in 1957, and that incident made Lim Yew Hock unpopular.
Split into simpler sentences: The other reason for his political downfall was that Christmas Island was administered by Singapore at that time. However, it was transferred to Australia in 1957, and that incident made Lim Yew Hock unpopular.