One reason to Latinize names is that it is hard to say some things in Latin if you don't.

Latin nouns have grammatical cases that indicate their role in the sentence. English has lost most of its cases (except for pronouns) and relies more on word order and propositions to convey the same information. For example, consider the sentence "She sent him the package by courier." Once you take out the cases and use the relaxed Latin word ordering the meaning becomes less clear: "She he courier package sent." It was typical practice to invent the declension of a foreign name, just so you can use it grammatically.

Another cause is just the passage of time and distance. Many of the works were only known through translations of translations of shifting languages.

Was there a specific example?