Someone asked me (about Karbala) if Allah had decided Karbala and Prophet Mohammad told each and everything, then what's the Hazrat yazid fault?

It's a discussion of qaza and qadr and not suitable to discuss in messages. In ust one sentence, in this way qayamat and jannat and jahanum all will turn out to be useless and thus the basis of Islam will become zero. Presence of day of judgement proves that we all have some power and authority to decide.