What do you think Bitcoin miners are doing? Cracking hashes.
What do you think the passwords are protected with? Hashes.
So it's easy to crack hashes passwords, takes a few minutes per password, as long as it takes to crack a new Bitcoin block (about 10 minutes) is how long it takes to crack a hashed password.
That's not quite accurate. Miners are tweaking one value in a block of data in order to find any password WITHIN THE DIFFICULTY. Finding a hash that is lower than a set value is far easier than finding a very specific existing password. Essentially, cracking the password would be solving the highest difficulty block possible. (Also, Miners are working on SHA256, much harder to crack than simple MD5...)