Here is an iconic Henri Cartier-Bresson image and while I recognize the excellent timing of the shot as the cyclist fills the "empty" spot in the frame can someone please help me understand why this image is composed so amazingly well? Can anyone explain it?

After watching Charlie Rose interview M. Cartier-Bresson and looking at his images I am in awe of some of the moments he's captured but in order for me to improve I'm trying to better understand his compositions.
Henri Cartier-Bresson, Hyères
Henri Cartier-Bresson, Hyères
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