Even if you start helping one group. The probability increases for others to get help as the momentum and knowledge builds up in total. This because challenges are similar in some sense.
Take refugee housing. Going from tents to housing units is a big improvement. Similar problems exist for the homeless. Here you also have tiny houses from living on the street.
The next challenge is income. Jobs and entrepreneurship. Here you could help the largest group by thinking big. Because the need to innovate you build up knowledge. As this process progresses you apply the knowledge to every group.