Wrinkles in diaphragms occur when the edge of the capsule- in this case the outer edge of one of the two diaphragm rings- makes hard, violent contact with the inside of the head basket.
A typical case: the mic is set down hard or dropped, and the capsule, due to its elastic mount, decelerates slower than the rest of the mic, and comes to a hard stop against the basket: the typical whiplash scenario.
When the edge of the diaphragm ring hits the basket, it can lose its original, perfectly round, shape and the original, even, diaphragm tension is lost in the process, forming wrinkles in the area where the diaphragm ring was hit and deformed.
In skilled hands, the diaphragm's distortion can be removed and the capsule restored to the original factory tension without any lasting damage or effect on performance of the mic.
P.S.: You can set down a mic hard, causing capsule damage, without also causing any visible body or head basket damage, especially during transport in its form-fitted case.