The main reason as to why Nijisanji is smaller in the west is that they have simple to many vtubers that make it impossible for a newbie to get in. It looks like Nijisanji En is going to run into the same problem. Hololive En has 11 members but with the Nijisanji wave 3 auditions that going up to ten members for niji. Then if we count the males that atleast 13 members already two more then holo.

Let's now look at the future in the year 2022 Nijisanji will probably have at least three waves auditions which would put them with nine more members and a total of 22 members which is insane. While holo en at max is 16 if they even decide to do auditions. The longer Nijisanji En branch grow the harder it will be for people to get into them due to having so many members.