Oh, no. It’s wasn’t anything close to a one-step process. That idea is an artifact of periodization: we show a passage from Beowulf and then one from Chaucer. There are many examples of early Middle English that, when taken together, show a gradual change. There are also regional differences, as can be seen in Langland’s Piers Plowman or Sir Gawain and Green Knight, which are quite different from Chaucer’s language, even though they were written roughly contemporaneously.
There’s also the false idea that no poetry was written in English between the Conquest and Chaucer. That’s just plain wrong too.