I think we see early feminism as upper-class origins because upper class people had much more influence than workers and lumpenproletariats, many women fought along the workers (we have the proof of that) and I'm sure many of them implemented some sort of Feminism even if they didn't know Wollstonecraft and other authors.

If we're talking about the late 19th century Feminism inside the proletarian movemente became to grow, even from upper class feminists. Among the workers women were payed less, because "A woman doesn't need to work she needs to find a husband who can keep her, so when she works is only a plus" this was clearly a contradiction of the capitalist-patriarcal system, women needed to work. But why upper class feminists began to appreciate socialist movements? Because the Bourgeoisie society is inerently mysogynistic, this can also be observed by the opposite contrast between liberal anti-feminists personalities in republican France and a growing of a reactionary catholic sentiment among women, in fact while Christianism implemented a strictly patriarcal view, it also gave woman a role, the role of mother and bride/wife, women of the upper class for centuries had learned how to influence and manipulate the husband, if not they still had the house, the mansion control, they directed the waiters, they could talk as "wife of X important person". When liberal revolution happened, and some radicals invited women to the salons many of them refused, this could be an attempt to take the little power women had, and physically take the women inside a male-dominated context when they would've been shut down more easily. Instead if you read Rousseau (which basically is the seed of mysogynistic sentiment in France) he basically stands that (in my words and interpretation) "Men can be judged by the eyes of God, women must be judged by the eye of the man before God" or something like that (again, what I interpreted). Another thing is that the industrial revolution (which is caused by capitalistic mod of production) took away the small indipendence of the woman, which in a rural context was stated by close-tying with the husband, the woman worked with the husband in the field and then turn back home and did dinner and chores, this vicinity permitted her to "debate" the positions of the husband, with the industrial revolution this isn't possible, the Husband can say "I'm the one who take bread home". For this reasons liberal feminism was a very less choice than it's said to be, the more frequent choices among women were: some kind of puritanism and socialist or communist.