Somi, Oh My Girl Arin, ZionT and Wonstein will form project group X4 as part of Busan's bid for the 2030 World Expo.
The World Expo is a giant exhibition/fair. Cities bid for it like the Olympics. One of Korea's themes will probably be related to kpop, so X4 is part of their bid.
So they are going for a power group with very popular artists in Korea (Somi has done some other government events in the past). Not to mention ZionT and Wonstein had a recent hit together with Merry-Go-Round.
video update:
It's OK. Sounds like a song made by government committee to appeal to all demographics except 50+ (which it probably was), so it doesn't have a clear focus. It even sounds like they tried to appeal to children with the simple melody in the first half of Somi's solo.