I find the Physics of Force interesting, but unexpected..
Suppose your car slides off the road into a ditch, and all you have is a rope to try to extract it.
If you pull on the rope, nothing happens.
If you tie the rope to a tree, and stand on the rope to deflect it a few feet, the heavy car moves a few inches, because the force is multiplied.
Similarly, a deflection of the MagSafe cord to the side will apply a very large force to the connector, which in most cases will cause it release.
As MrHoffman points out, if any part of that deflecting force is up or down, the connector will release even more quickly.