This thought came across my mind when I learned about famous humans throughout the history of human civilization. I noticed that influential people who lived thousands of years ago, somehow had first names that are still common today. For example, Julius Caesar, Mark Antony, Alexander the Great, etc. all had first names that are commonly found today. On top of those examples, a lot of names that appear in the in the Bible are commonly found today as well. I looked all over the internet for an answer, and it’s been burning on my mind.
But they have. You've mentioned famous people, whose names tend to be remembered and used, and a book most Europeans were familiar with.
Old English, for example, had many names that were, over time, changed [e.g. Chad, from Ceadda], or simply forgotten, like Cynebald.
Sometimes names were forgotten after invasions - see for example, nobility turning to Norman names after 1066. https://www.bbc.com/news/magazine-10776581
Sometimes because names became hopelessly old fashioned and for whatever human quirk never turned fashionable again - such as Myrtle which was #32 in the US in 1900, and hasn't been in the US's top 1000 since 1965. [Source: ssa.gov's baby name lists].