Among social species, helping one individual can incidentally increase your chances of survival. If this process is repeated enough times, you get a species that is altruistic in nature. You can see this among many social species, especially other primates and dolphins.
Organisms whose success is a demonstration of their failure to die off prove that altruistic acts among agents with parallel goals more often benefit both, without a Boolean winner and loser. Among agents with parallel goals a win for both provides more sustainable success than a win for just one.
Evolution cannot be reduced to that level. If you help me push this big rock off my yard today, I'll do the same thing for you tomorrow. Both increase their survival. Humans have developed many skills to enable groupwork, like a keen ability to detect non-contributing members.
Social species maintain altruistic behavior to form groups, and outcast the members which don't return the favor. If an organism isn't social in nature, then it has to have traits that allow it survive which altruistic species don't, but any social species which is social is also altruistic.