Because the flywheel can then be the fan. Of course nobody was going to notice this answer on the FP.

Here’s a view from the back, under a Renault truck:

Weirdly, flywheel fans were sort of common for a period of time around 1910. Although most cars kept the radiator up front, and the engine was “sealed” with an under-tray and an air-tight hood to keep air flowing through the engine compartment, and out the back, through the fan.

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Weird huh? Renault did the smart thing and put the radiator near the fan (instead of what everybody else eventually did, which was put the fan near the radiator).