Andrew Z. answered 03/21/19
Experienced MFA Grad Teaching English, Literature and Writing
You are right that the orthography of English is related to its rich history and variety of influences. Early English actually sounded very Germanic, almost like Norwegian. It was very phonetic and every letter was pronounced in a word, just like in most Germanic languages. Because English has so many different sources for its vocabulary (Latin, Saxon, Celtic, Norman, etc.) it contains a multitude of words with different origins. Even though these words come from different origins, they must still conform to the orthography and alphabet of English, therefore they use the same digraph in different ways. That is why an originally Latin word like "pageant" uses the digraph -ea in a totally different manner than a Germanic word like "break".