Complete Rube here...
If the everyday language of the ruling class is essentially different from the hoi polloi (Norman French vs Saxon English), how does that shape the development of that culture? Or, flip that idea on edge, how does society get shaped if the ruling class language is very similar to the general population (Germanic variant vs Germanic variant) ?
Culturally, you typically won't see too much change outside of politics (depending on what system the invaders bring to the table) and perhaps concepts of manners (i.e. why many English words are vulgar for objectively arbitrary reasons, whilst Romance synonyms are "nicer"
). Languages, above all,
DO NOT CHANGE FROM ONE BRANCH TO ANOTHER. I'm not trying to be mean, but that's a misconception that gets me riled up every time. If you have Language A being suppressed/replaced in upper circles by Language B of the conquerors, you'll result in Language A getting influences from B without actually
becoming B in any meaningful sense. If alterations in syntax, morphology, etc. do happen, you end up with a creole, not a switching of one language to another family (which isn't the same thing, but rather a dumbed-down new language which isn't really one or the other). If Language B is close enough to Language A, you end up with borrowings of vocabulary (as well as grammar, et. al.) but there's no threat of linguistic shifts between language families, since in that case they're already sibling tongues and already share tons of cognates and similarities.
Again I can make a slight remark here. French as a language of the upper class and thus a prestige language, has a longer, but also older history in English. It doesn't mean that German and Dutch didn't have a period, where the upper classes considered French as prestige language.
In Dutch French influence started to increase in the late middle ages, especially the Burgundian era was important for this.
Once French became the European prestige language, Dutch and German followed the European trend (including upper classes speaking French with each other) until the age of nationalism.
Noted. However, the point I was trying to make was that the lack of a Norman Conquest doesn't inherently mean English shall have a smaller vocabulary on the whole, it just won't have those OTL Normanisms during the post-1066 era. Who's to say that other French dynasties won't have a lasting influence on English, or the Flemings/Danes/etc.? And truly, things there aren't words for as of yet can come both from without (i.e. Latin) or within (making new sayings and "kennings") even in OTL Old English, which is likely to go on and/or grow even if William loses his bid for the Throne.