Who do you think is more successful/ safer: the humpback whale that let’s its kin die, or the one where they stick together against predators?
To generalize, draw on your “experience” (movies, thought experiments) from crime, business, sports, society etc.
‘Altruism’ only appears so on the individual’s level but there’s zero surprise this is an evolutionary advantageous trait from a species perspective, so, frankly, I never understood why we make it out to be that mystery.