Science is based on the principle of the inference to the most plausible. When you have multiple theories explaining a phenomenon, the one which makes the most sense with regards to the gathered data is deemed THE explanation. That is, until another theory comes with more compelling data and evidences.
Example: the “static universe” cosmological model
Science is basically our best understanding of the world. Doesn’t mean it’s 100% true, but it’s how far we got.