Why do cats knock things over? Although you may think your cat is malicious (and it probably is), the more logical reason is that cats want your attention. Just like little kids, cats don’t know how to express themselves using words. So they rely on action instead.
By knocking something over, cats learn that it gets your immediate attention. So you inadvertently reward your cat by giving it attention when it knocks something over. Then your cat gets what it wants and you get to clean up whatever broken item the cat knocked over.