That's assuming someone is trying to brute force a system 'from the outside', without having access to the list of password hashes for the system. In reality such attempts rarely if ever happen and they are easily defeated by using rate limiting and other techniques.
The problem arises when the attacker has a list of hashed password and is running checks against that list. In those cases, the fact that a password is random won't do any good as the program knows which password hash it is trying to crack.
Furthermore, there is no "de-hashing". Password cracking software is actually hashing commonly used words, letter combinations and/or even random characters, and comparing the output of the hashing operation with the password hash that it is trying to crack. Cryptographic hash functions are unidirectional and cannot be reversed, you can only try to hash raw data and hope to produce a hash which matches the hash you're trying to "reverse".