To check-mate, confound. Used by Shakespeare in the sense 'to confound;' as in "My mind she has mated, and amazed my sight;" Macbeth I 86. It is the same word as is used in chess, the true form being check-mate, which is often used as a verb.
The question, "Why does mates?" takes on neither a subject nor an object, and therefore must be thought of as a general question as to why there exist thing(s) that confuse or, more accurately, instigate a state of confusion.
The fractal nature of existence by definition makes it so that parts of existence are intangible, invisible, unimaginable, etc. This is because a being capable of cognition, and perhaps therefore capable of comprehension, must exist on a certain scale of the universe. No matter what scale it exists on, there will always be an infinite number of scales less than and greater than its own level. The smallest scales are components of the larger scales, so without a comprehension of these, there is no comprehension of the scale, even, at which said being exists upon. In order for information from the smallest scales to reach to being's scale, the information would have to rescale itself an infinite number of times, which is impossible. Information cannot be preserved entirely even after one rescaling. Therefore, any being will not understand its surroundings. An even stronger fact, however, is that no being will be able to know what exactly it understands, if anything, and the extent to which it has a so called understanding. Human beings are special in that they can, in rare instances, deny that they understand something.