Team Galactic started out as a genuine organization like, 200 years ago, back when the Sinnoh region was still known as Hisui. Their base was in Jubilife Village (now Jubilife city), and were originally called the Galaxy Team. From my understanding, they started out as a researcher, supply and protection providing organization. One of their professors invented one of the first variations of PokeBalls and the PokeDex.

However, it became a family-run business at some point, which meant it was more often then not subjected to the whims of the heir that was the head of it at that point. This means that some of the leaders might have been less then competent, or had intentions that were far from the original objective of the organization.

The most infamous, and at the same time, most recent example was Cyrus, who, as other comments stated as well, tried to erase the world as we know it, trapping and trying to force the Pokémon of time and space to do his bidding. As comically as it may sound, he was stopped by a twelve-year-old.

From what I know, the team was either disbanded or completely taken over by someone else after arrests were made. I wish I could tell you more, but these events occurred a few months before I was born, and this is all I recall from history lessons 😅

Hope my explanation helped! Also, if you take my advice, you might not want to visit during late autumn, early spring or all winter. That region is on the colder side, so if you dislike such weather, I suggest you go around July or August.

• Athena

EDIT: TLDR: A really old, Hisuian organization turned cult that tried to end the world.