It seems to come down to how well the models can end up with similar results to what we see now after we run them 13 billion years forward. But I know there are a number of problems with the ones we have now for the big bang theory. And it does seem quite simplistic and even a bit crazy to simply observe expansion and conclude it all used to be a single point. That's not to say it couldn't be right, but I think it's good other ideas are being explored!