Darwin didn't fully understand evolution he came up with the theory.
In a phrase; the mechanism of natural selection.
Darwin's explanation for the fact of evolution was better than Lamarck's explanation and fit the fact of evolution. Natural selection solved much of the species problem, but acquired characteristics did not have the empirical support and explained nothing in the end.
What is the mechanism that causes evolution. Both knew evolution occurred and occurs but did not know how or why. Lamark's " desire to evolve " and " acquired characteristics " failed to explain evolution. Darwin's theory of evolution by natural selection was the better explanation.
'Evolution of the fittest by natural evolution' is attributed to Darwin and Wallace. An alternate phrasing might be 'Failure of the least-fit by ... ', which equally (or better) explains the results.
Evolution
By proposing a mechanism for evolution, natural selection, that explained much better than his predecessors how evolution came and comes about.
Better known as "adaptive radiation", it is independent evolution from a population of a species that has become geographically isolated from its parent population.
Natural Selection is what Darwin believed was the cause of evolution.
how has Charles Darwin influenced people about modern views of evolution
Charles Robert Darwin, though evolution was already known. Darwin came up with an explanation for evolution. Called the theory of evolution by natural selection.
Darwin invented the theory of evolution
Darwin only had one theory of evolution, and he defined it in his book On The Origin of Species.