All the other Alexanders are just imitating

!look, there were already great answers, so there was room for a joke one!<

Alexander is a common name, but it depends on context, if you say “at the time Alexander conquered X” most people would understand, but if you say “Alexander was here” you might be talking about a work college.

There’s not only one Caesar, while you probably beat Julius Caesar, Augustus, Tiberius and others were also “Caesar”, and you might referring to any of them. For example, “give to Caesar what is Caesar’s” does not refer to the same Caesar you probably meant.

Slim shady is a made up name and it’s way more specific than <common name> the <common adjective>.

Charlemagne is short for Charles Magnus, or in English Charles the great, so that’s exactly the same.

Attila is a very unique name, I’ve never met nor heard about any other Attila so the name is disambiguation enough, but it’s likely that if that is a common name in some country they have an extra qualifier to it, I’ve heard Attila the Hun, but there might be others.

There’s nothing special, if a name is common you need disambiguation, if a name is overly specific you don’t, same reason why we have last names, “I met with John the other day”, “which John?”, “The Smith”, “Ah yeah, John Smith, not John the son of Richard”, “No, I haven’t seen John Richardson in a few weeks”.

There’s only 1 Caesar

Not necessarily. I originally thought the phrase “Render unto Caesar what is Caesar’s” from the Bible referred to Julius Caesar, but apparently it refers to Tiberius.

Though in modern times “Caesar” almost ubiquitously is referencing Julius