In early Islamic literature it is said that Hiraculus was able to have a discussion with Abu sufian in Damascus where he probes the prophet's uncle about the message of Islam. Muslims will believe that hiraculous himself was interested in Islam but he couldn't turn his back on the empire's already established culture and religion. Maybe having Heraclius as a Muslim convert in this timeline would be an interesting take.What i was originally asking was for a possible Muslim Emperor without a conquests, but all the ideas here are super interesting. Thats the great part about "What If"s.
History has many stories to tell and many lessons to learn from. Mistakes made in the past can be avoided by the one who studies and reflects today.
Sahih al-Bukhari 7 - Revelation - كتاب بدء الوحى - Sunnah.com - Sayings and Teachings of Prophet Muhammad (صلى الله عليه و سلم)
Hadith of the Prophet Muhammad (saws) in English and Arabic
Some commentary: https://aljumuah.com/the-hadith-of-heraclius-part-1-abu-sufyan-enters-the-roman-court/