[Facts] Re: How are names ending in cia pronounced as sha in English?
This isn't specific to names. Consider the pronunciation of "special," "social," "musician," "physician."
Of course there are exceptions, such as the word "pronunciation" itself.
I don't know that there is a specific why. English spelling is quirky and only partially phonetic. And many people named Lucia, for instance, pronounce their name "loo-see-a" or the Itaian way, "loo-chee-a"