Complex sentence: Unlike Stock car racing, the exact origins of Banger Racing is not as clear; as short oval racing became popular from the mid 50's the crashing aspect of the Stock car formulas of the time appealed to the crowds and drivers.
Split into simpler sentences: Unlike Stock car racing, the exact origins of Banger Racing are not as clear. Whilst short oval racing became popular from the mid 50's, crashing was found to appeal to both crowds and drivers.