Titanic's sinking marked the darkest and brightest night in maritime history, Though more than 1,500 people died in this international tragedy, the Darwinian notion of the 'survival of the fittest' was rejected in favor of the age-old Christian doctrine that the 'strong sacrifice for the weak.'
It was a good idea to let the children and women to leave the titanic first because they are vulnerable and the chances of them surviving are slim. Another reason why it was a good idea is because it is logically the best thing to do. It was also a good idea because it significantly reduced the number of casualties from the incident.
just like the other answer said, it was good because they were vulnerable. second, it could be because women can actually give birth and reproduce and children can grow up to do the same. i hope this helped :)