I remember Adam addressing this in a bit of depth in his second Chatterbox interview. I'll post that, since it's pretty interesting. He said a lot of it, he thought, had to do with the marketing campaign; there would just be posters that said "RENT" and the date, and that the campaign assumed that people knew what this American phenomenon was. But, they didn't, and if they did, it felt like the campaign was just pushing it as this big, bad American musical that you were
supposed to be familiar with. His take was that if they didn't know what it was, this sort of strategy certainly wasn't going to make them care to check it out.
He also seemed to think that other parts of the show were sort of lazily done because they did have OBC members there, and that they were expected to shoulder the production... poor direction, etc. He said that some of the new cast members just didn't have their hearts in it, and really didn't understand very well the weight of what they were doing, and told a story about one of the girls who played Mimi, saying she was often drunk.
I don't know enough to offer my own explanation, anyway, but I always enjoy his opinions, since he's so honest.
A work of art is an invitation to love.