Complex sentence: For a while Lisberg managed Wayne Fontana after he left the Mindbenders, by which time guitarist Eric Stewart had come to the fore as lead vocalist on A Groovy Kind of Love, a 1965 hit that reached number 2 on both the U.K and U.S. charts.
Split into simpler sentences: For a while Lisberg managed Wayne Fontana after he left the Mindbenders. This allowed guitarist Eric Stewart to come to the fore as lead vocalist on A Groovy Kind of Love which in 1965 reached number 2 on both the U.K and U.S. charts.