Intelligence does not increase your reproductive fitness past some baseline number, as a result we see regression to the mean.
Intelligence has improved out survival to such a degree, that you don't need to reproduce as much as an average bear to successfully pass on your genes.
Survival is not just about fucking more. As a matter of fact, having 5 children is counter-productive because they consume so much resources and require so much care. If your one child survives into adulthood, finds a mate and successfully breeds, then your evolutionary duty is done. Any more and you are introducing stress on to the environment to the detriment of your offspring. If you notice driven, successful people tend to not have any issues with passing on their genes.
Contrast it to your example of a bear: They need to breed more often, because that intelligent, top-of-the-foodchain predator might shoot and skin your offspring before he/she gets a chance to pass the genes further. No matter how successful the bear is, it is just a matter of pure luck whether it will come across a bloodthirsty hairless ape or not.
Compare the numbers: There are much more humans in the world than bears.