Hololive has always treated their male talents on the JP side as an afterthought compared to their far larger and more successful female talent roster, with Holo’s male and female branches remaining largely segregated with minimal collabs in order to appease fans of idol culture. Nijisanji, meanwhile, has from the beginning promoted co-ed talent interaction and collaboration, with some of their biggest talents being male themselves. When you consider each company’s approach to interaction between talents of opposite genders, it makes sense that Nijisanji’s EN males would have a much larger presence and therefore more subs, because they’re treated with the same importance as female Niji talents unlike in the female-dominated Hololive.
For reference, I don’t really watch Niji because I don’t like watching males, and Hololive fits my interests better. Holo and Niji each appeal to a different demographic.