What was one of the problems with the theory of inflation and the multiverse when it was first conceived?

One of the main problems with the theory of inflation and the multiverse when it was first conceived was its lack of testable predictions. While inflation provided a plausible explanation for the uniformity and structure of the universe, the idea of a multiverse suggested that our universe was just one of many, making it difficult to validate or falsify through observation. This led to criticisms regarding its scientific rigor, as theories should ideally be grounded in empirical evidence. Additionally, the vastness of potential universes in a multiverse scenario raised philosophical questions about the nature of reality and the limits of scientific inquiry.