It seems like scholars use different names as a form of historicization. So Augustus didn’t fight a civil war with Mark Antony. It was Octavian who did so. Popes are almost always referred to by their former names when talking about their pre-pope days. I guess you could argue that papal names function more like a title than their actual names. So Robert Prevost didn’t stop becoming Robert Prevost while Pope Leo XIV is a papal name that’s not his real name.

It gets weirder for someone like Malcolm X. Technically, “Malcolm X” is the name the man adopted from the time he joined the Nation of Islam to when he left the Nation of Islam. So, “Malcolm X” the name points to a particular historical period within the man’s life just like “Malcolm Little” or “Detroit Red” were as well. The name the man himself actually wanted to be known as is El-Hajj Malik El-Shabazz. That’s his real name. Most people call El-Shabazz “Malcolm X” and some people use “Malcolm X” alongside “Malcolm Little” and “Detroit Red” as a shorthand for “when El-Shabazz was a kid” or “when El-Shabazz was part of the Nation of Islam.” It’s mostly Black Muslims and Pan-Africanists who actually call El-Shabazz the name he wanted to be remembered as.

Names are just weird.