Complex sentence: Multiple projects for the fledgling city of Torrance probably prompted the move.He returned to live in North San Diego County in the 1920s, but his work slowed considerably due to lingering illness, changing public tastes, and his diminishing willingness to compromise with clients.
Split into simpler sentences: Multiple projects for the fledgling city of Torrance probably prompted the move. Gill's work slowed considerably after 1920 or so due to lingering illness, changing public tastes, and a lessening desire to compromise with clients.