Question: why yazid killed imam hussain?
Answer: Following his accession, after Muawiya's death in 680, Husayn and Abd Allah ibn al-Zubayr refused to recognize him and fled to sanctuary in Mecca. When Husayn was on his way to Kufa to lead a revolt against Yazid, he was killed with his small band of supporters by Yazid's forces in the Battle of Karbala.