if i remember correctly, mawlana sa'eed as'ad said this couplet is by mawlana muhammad ali johar. he modified it slightly: qatle husain asl meiN marge yazeed hai islam zinda hota hai bas karbala ke ba'd he said there will not be another karbala. he may also have said that husain radiyAllahu ta'ala anhu had made islam alive till the final day, hence, islam zinda hota hai bas karbala ke ba'd.
Imam Husain radi Allahu a'nhu is Alive "Qatle Husain asl main marghe yazid hai, Islam zinda hota hai har Karbalah ke ba'd" "The martyrdom of Imam Husain was in reality the death of Yazid, Islam is revived after every Karbalah" After hardship comes ease.