I will look at why they are so different.
Ancestry
Legendary heroes often have royal and/or divine ancestry.
Charles Darwin came from an aristocratic family, and one of his grandfathers was a noted biologist, but Abraham Lincoln's parents were very ordinary people.
Infancy and Childhood
Someone tries to kill the hero in his infancy, but he is rescued, and he is often raised in another land by foster parents. The hero's would-be killer is sometimes tipped off by a prophecy of the hero's coming. Aside from that, we learn little or nothing about the hero's childhood.
Nothing of the sort had happened to either CD or AL, and we have learned some details of their childhoods. In fact, this is rather general. We don't have lots of stories of villains trying to kill baby heroes:
- Southern plantation owners vs. Abraham Lincoln
- Fundamentalists vs. Charles Darwin
- Rabbis, Jewish bankers, and Jewish Marxists vs. Adolf Hitler
- Psychiatrists vs. L. Ron Hubbard
- Oil-company executives vs. Muammar Gaddafi
We also don't have even the tiniest hint that the hero was coming.
Adulthood
The hero defeats some big villain, he becomes ruler, he marries a princess, and he has an uneventful reign where he issues laws.
The closest thing to big villains for AL was opponents in political contests, and CD did not even have that. AL's career as leader was *very* eventful, since he led the North in the US Civil War. CD's career was also not very eventful. Even his trip aboard the Beagle was not very dramatic. A possible exception is when he discovered that Alfred Russel Wallace had also worked out natural selection, and he decided to rush into print with what he had worked out by then.
Laws? Making evolutionary biology a rigorous science certainly qualifies as a sort of law, and AL passed some notable laws, like establishing land-grand colleges, financing railroad construction, and freeing the slaves.
End of Life
The hero is often repudiated and dethroned, and he soon dies a mysterious death, often at some elevated place. Though he is not often buried, at least not persistently, he may have several tombs in his honor. He is not succeeded by his children, if he has any.
Abraham Lincoln was not repudiated. Instead, he was shot by some disgruntled Southerner, though he was shot in an elevated sort of place: a theater box seat. Charles Darwin was not repudiated either. In fact, he was buried in Westminster Abbey, a great honor.
Some very notable people have indeed been repudiated: Tsar Nicholas II, Richard Nixon, Mikhail Gorbachev, and Muammar Gaddafi. However, Napoleon Bonaparte and Adolf Hitler were not repudiated, despite having been defeated by their opponents.
One of CD's children went on to become a noted scientist, though not an evolutionary biologist. None of AL's descendants have been anyone notable, however.
