Vilna Goan says converts are the neshomos of those individuals of the Nations of the World that accepted the Torah.
Chida says most converts come to Judaism from Esav not Yishmael
Yishmael has the word Nishma in its word (Yishma/nishma)
Esauv has the word Nasse (Asse-v)
Because Esauv gave more ‘sparks of holiness’* then Yishmael (Naase) they are Zoche to have more converts to Judaism
* see Zohar, Esav it says Zorach MaHar Seir (a greater Loshon of light) then Hofia MeHar Paran (a lesser Loshon of light).