Path To Paradise

"''Whoever treads a path seeking knowledge, Allah will make easy for him the Path to Paradise." -Sahih Muslim''

Point of divergence: What if Muawiyah I did not appoint Yazid as his successor and instead opted for an elective caliphate?

Things to consider:
 * Muawiyah I of the Umayyad clan does not appoint his son, Yazid, as the successor to the Caliph position which upstarted the Umayyad Caliphate and ended the Rashidun Caliphate. Opting for an elective caliphate, the likes of which the Rashidun had remained for decades prior, Abd Allah ibn al-Zubayr is elected as the seventh Caliph of the continuating Rashidun Caliphate, with Muawiyah I being remembered as the sixth.
 * The Battle of Karbala does not occur due to Muawiyah I not claiming Yazid as his successor.
 * The Sunni-Shia split is resolved.

Timeline

 * First Century AH