Did I miss something? When did the Theory of Evolution become the Law of Evolution?
In short, evolutionary theory as a complete explanation for biological diversity (and the origin of life if you include abiogenesis as part of evolutionary theory) is just a theory with incomplete evidence to consider it a fact. Evolution as the process of life changing through variation and natural selection though is a fact. Explained more here: Fact and Theory
Evolution is a observed fact. Evolutionary Theory is what explains how and why evolution occurs.
Yes you did miss something, the definitions of fact, theory and law.
Facts are observation, or data points. Theories are the explanations of those facts. Laws are descriptions. Theories do not 'graduate' to laws because they serve different purposes. Theories do not 'graduate' to facts, but are based on facts.
Yes, you wer asleep in your science classes when the qualitative difference between theories and laws was explained. I bet you think theories become laws when they get solid enough. Wrong..... Theories and laws serve different purposes. Theories are much more interesting and important than laws, which are usually just observations of simple empirical relationships in nature with no implied understanding of mechanics behind them.
The so-called law of faunal succession was known decades before Darwin. This states that a particular kind of fossil is confined to a particular layer of rock, and that as the rocks become more recent, the fossils gradually become more and more like living animals.
Buffon, Lamarck, and others tried to explain this, but without success.
Darwin's observed that 1) by only allowing individuals with desired traits to live to breeed, animal and plant breeders had created innumerable varieties of dogs, pigeons, horses, etc., and 2) in the wild, only a small percentage of animals live to breed.
His great insight was that no other mechanism was necessary to explain the law of faunal succession, and thus to account for the variety of living things today. In fact, he hypothesised that all life could be traced back to a common ancestor.
Combined with modern genetics, voila, the ToE.