Darwin connected the specialization of finches to two bodies of existing work — animal husbandry and the nest hierarchy of biology, by explaining they’re both outcomes of reproductive selection.
Einstein connected the idea of Galilean relativity to Maxwell’s equations to explain why Michelson-Morley behaves how it does.
Which itself is a derivative of the "great chain of being" ontology which tried to explain the continuous gradation of structures in the world. Ideas like "missing link" appear within this worldview before Darwin's theory[1].
Darwin connected the specialization of finches to two bodies of existing work — animal husbandry and the nest hierarchy of biology, by explaining they’re both outcomes of reproductive selection.
Einstein connected the idea of Galilean relativity to Maxwell’s equations to explain why Michelson-Morley behaves how it does.