Vowel shift. Common among all living languagues. Also remember that most English speakers of Hebrew are descended from Yiddish speakers, and Yiddish since it was largely an oral language (Yidden spoke Yiddish, but wrote in Hebrew) was more likely to have vowel shifting.
Note that Ha-Shem and Moshe refrained from including International Phonetic Alphabet notation, and did not include a sound recording of how Hebrew is supposed to be pronounced.