Complex sentence: As a young man, Johnny Longden worked in the mining industry but with a love of horses and horse-racing, his small stature led him to leave Canada in 1927 to seek opportunities as a jockey in California's burgeoning racing scene.
Split into simpler sentences: As a young man, Johnny Longden worked in the mining industry. His love of horses and horse-racing led him to leave Canada in 1927 to seek opportunities as a jockey in California's burgeoning racing scene.