Movement doesn't make sense when we can't predict or explain it. Based on our understanding of gravity as confirmed by observations of our solar system we expect to see galaxies do X but instead they do Y, and then we collectively fail to identify a simple explanation like bad math or a bad assumption.
In one sense this is a vindication of our application of the scientific method and the way we make theories: a bad theory wouldn't be able to be checked, whereas a good theory can make precise enough claims that when a limitation is found (such as when our predictions about reality do not match our observations) that the results of the check are clear.
In one sense this is a vindication of our application of the scientific method and the way we make theories: a bad theory wouldn't be able to be checked, whereas a good theory can make precise enough claims that when a limitation is found (such as when our predictions about reality do not match our observations) that the results of the check are clear.