Another factor was the profound inefficiency of the fixed pitch propeller at low speeds ie take off. The prop had a massive pitch to suit the high speed flight of the race. That high pitch meant the prop was not very effective at producing thrust at low speed, leading to poor acceleration which, in turn, caused a very long distance needed to take off. Unlike now, there didn't exist 3, 4,5 or even 6 km long runways - except ready made ones on bodies of water.