Last names weren’t really a thing until very recently in human history.

That’s why a lot of last names are places or jobs.

You were Chris the Farmer, or Chris from Cleveland. And when your king wanted a last name to tax you more accurately, you likely didn’t give a fuck and just said whatever.

But the thing is people would say names/jobs in different languages.

An immigrant from Germany who spoke mostly German would say “My name is John Deutsch”. if they were fluent in English they may say “My name is John German”.

Same guy. Describing himself the same way, just in two different languages.

Fo Colombus specifically, that’s not even his name in his native language. It was Columbo, which meant Dove and given mostly to orphans, but at least his dad had the same name. Whenever last names became standard, Columbus’s oldest living direct ancestor was an orphan

So like, it’s not asking why just the places named after him are different, it’s why he had different names.

And the answer is people just really didn’t care that much about names until very recently.