I'm a bit iffy on if this question belongs here, but I choose to put it here because there is probably some very strong historical ties here ( And I don't know where else to put it. Not AskScience, and DEFINITELY not AskReddit ). So feel free to redirect me if there is a better place this deserves to be.
But onto the question: Why did languages develop differently in different areas of the world? Why did vulgar latin speakers in France develop French, and why did the ones in Spain develop Spanish, a completely different language? Or more specifically, what are the factors which determine what a language is "like"? I know isolation and time both play significant roles, but that doesn't really explain why German is so a guttural, or why Italian is so 'romantic'?
Your question doesn't look to be finished. But the best subreddit where to ask this question is /r/linguistics. The answer to your question is very simple: it's external influences like borrowings and random language mutations, like vowel shifts (or sound change in general). There exists no reason for the shifts, but they have their rules. For more specific information ask the linguists.