Multiple brackets - ))) - are used for LOL, to express laughter or humour. This is not to be confused with ((( ))), known as a far-right symbol directed against Jewish people. Overuse of brackets ("))))))") may suggest that something is funny, something is ridiculously ironic, or the writer may be insincere.
Multiple brackets with zeroes - ))0) - are like the usage of !!1, to express a strong emotion.