Anti-theist here, religion in all it’s forms is a blight on humanity, but let’s not muddle the waters with misused vocabulary.
The difference between a cult and a religion is not the number of believers, it’s how much they enforce groupthink, how hard it is to leave and if they are based around a charismatic leader who profits directly from the imposed sameness and thought control. Generally cults:
Rush you into joining and discourage or disallow questions.
Followers are encouraged to worship a specific group leader.
Leaders dictate in great detail all aspects of followers’ lives.
Followers are personally monitored to ensure they’re following guidelines.
Methods of control are used to keep members close.
That’s how, for example the catholic church isn’t a cult but scientology is. The sharp surveilance and strong measures in place to prevent deviancy make all the difference. It’s easy to leave catholicism, but leaving scientology can even be dangerous.