The short stride greatly reduces the angle of your foot with respect to the floor/ground. That helps because there is very little distance before your foot and heel are firmly planted on on the floor/ground. When you take longer strides, there is a great angle of your foot with respect to the floor/ground and the only support you have is on the very small heel. Exceedingly strong ankles are required to prevent rolling over before your entire foot is on the floor/ground.
Watch Jessica and Donna on the SUITS TV program. Their arm motion is not parallel. The forward movement forms a V at the front. That helps the hip movement when walking.