Galar was a little weird. Like in other games, Galar has a gym challenge in which trainers tackle each gym around the region for their badges. The gym leaders, I believe, were trainers that had obtained the badges on their adventures at some point prior to the events in Sword and Shield later becoming gym leaders themselves. That, or at the very least, pupils of those gym leaders who inherited the position of gym leader through some unknown official process. Rather than an Elite 4, the Pokemon League sponsors a periodic tournament in which those with the requisite gym badges and the gym leaders themselves would battle to see who was the strongest out of the bunch. Whoever won the tournament earned the right to battle the champion of the Galar region in the hopes that they may claim the title of champion.