What are the primary causes of this?
The steam and other hot gasses that were puffing the cookies up either escapes or condenses. Without heat to create more steam, the cookies deflate.
You get exactly the same effect with bread, quiches, and other baked goods. You can hear bread start to make a crackling sound almost as soon as it comes out of the oven, and the sound continues for some minutes until the bread has cooled a bit. Quiches are always quite puffy looking when they're in the oven, but they start to shrink a bit as they cool.
If you want your cookies to shrink less, you might try cooking them at a slightly higher temperature, or cooking them a bit longer, or perhaps not chilling them so much prior to baking. Bumping up the amount of egg white in the cookie may help, too. The idea is to get the structure of the cookie to set a bit more by the time you remove the cookies from the oven. That will, of course, cause the cookies to be less chewy and more crunchy.