Complex sentence: According to Darlene Love, Ronnie Spector was not able to put as much emotion into the song as needed, so Love was brought into the studio to record the song instead, which eventually became a big success.
Split into simpler sentences: According to Darlene Love, Ronnie Spector was not able to put as much emotion into the song as needed. Instead, Love was brought into the studio to record the song which eventually became a big success.