That's not the explanation; it's the cause of the confusion.
Wrong.
The cause of the confusion is that the questioner is an easily confused idiot. "How come apes are still here?" is an inane question on many levels. First, humans
are apes. Second, the particular ape that is the actual common ancestor of humans and chimps
is extinct. Third, even a fool can see that humans don't compete with other with other primates by trying to fill the same niche.
The flip responses given by Dr. Adequate, PaulK, and others in this thread ought to be sufficient to see that the question misses the mark. Someone who cannot see that the question is facially ridiculous given those answers is never going to understand a more detailed answer. Don't waste your time.