Galileo’s genius was that he was a brilliant experimental physicist, and was also able to form ideal models from his experiments in a non-ideal world.
For example, his experiments involving rolling bearings down slopes lead him to realise that acceleration for all bodies is actually the same, but that less dense objects will be more impeded by atmospheric resistance than denser ones. This famous footage confirms his idea.
He also happened to discover prima facie evidence that the geocentric model of the universe was wrong…