My experience (as someone connected to both the rationalist and Oxford/Giving What We Can clusters as EA came into being) is that its birth came out of Giving What We Can, and the communities you mentioned contributed to growth (by aligning with EA) but not so much to birth.
My experience (as someone connected to both the rationalist and Oxford/Giving What We Can clusters as EA came into being) is that its birth came out of Giving What We Can, and the communities you mentioned contributed to growth (by aligning with EA) but not so much to birth.