Complex sentence: The chain drive, coupled with gears to multiply the revolutions of the pedals, allowed much smaller wheels and replaced the need for the large, directly peddaled front wheel of the penny-farthing, and made cycling much safer, and therefore much more popular.
Split into simpler sentences: The chain drive, coupled with gears to multiply the revolutions of the pedals, allowed for much smaller wheels, and replaced the need for the large, directly peddaled front wheel of the penny-farthing. The safety made cycling much safer, and therefore much more popular.