Those that are relatively simple-minded want to believe, somehow, that life is really a battle between them and everyone else, so to speak, and therefore a survival of who thereof is the fittest. If, indeed life is truly a survival of the fittest, then this would imply that life is ever evolving in a direction in which humankind is thereby constantly advancing and therefore consistently building successfully upon that which has come before, because, it so follows, it is getting ever fitter; but the world as it really is, is not indicative that the fittest have survived and that the weak have been conquered, or even that the fittest are actually in charge. While it might seem to make sense, that the fittest should be the exclusive winners, this discounts how complicated as well as how nuanced, life really is, so that one's survival or even advancement is based far more often upon the interplay that is generated day-by-day with other people, then just one's own skill set.
Additionally, it is a mistake to believe that a bunch of superstars, somehow always make for a better team, such that they are superior to a diverse group of people that though less talented in aggregate, are able thereof to work together and to meld over time into one solid assembly; for the former typically have prima donnas within their domain and prima donnas usually don't want to bother doing what needs to be done to work well together as a winning team; whereas the later is all about doing what needs to be done, for the betterment of the team, which ultimately benefits each member of.
So then, those that are simply about their own self are essentially undercutting one another, in order to get ahead, thereby sowing the seeds of their ultimate mutual destruction, for each personage has their own separate agenda, and thereby they conflict one with another. On the other hand, those that are able to bond together, are the ones that understand that being of service one to another, and thereby creating unity through that voluntary mutual aid, are the very people that are going to be successful, more times than not, because each person entwined together, makes for a very strong bond, that is well nigh unbreakable, against even the strongest of gales.
So in fairness, it can be said that the biggest survivors aren't necessarily the fittest, but rather are often those that have the perception and the wherewithal to recognize that having found a purpose worth living for, or even that worth dying for, provides the motivation and thereby the important goal to focus upon that actuates people to really get things done. This signifies that a simple belief in the survival of the fittest, is belied by the fact that in reality, those that make the most progress in life and for society are actually those that understand the necessity as well as the importance of finding something in their own lives, that is bigger than just their own self, and thereupon make the effort, typically with others of like-mindedness to create the change that is needed for the betterment of not only their own self, but indeed, for humankind.