What turned old English into middle English?

Old English evolved into Middle English primarily due to the Norman Conquest of 1066, which introduced a significant amount of Norman French vocabulary and influence into the English language. This period saw a shift in pronunciation, grammar, and syntax, as well as the simplification of inflectional endings. The merging of Anglo-Saxon and Norman cultures facilitated this transformation, leading to a more diverse and flexible language that eventually became recognizable as Middle English. Additionally, social and political changes played a role in the linguistic evolution during this time.