He kept the secret for so long that he’s almost out of time, and he has no choice but to.

This is actually a lie, though as Rose will eventually reveal to Leon during their meeting at Macro Cosmos tower in a desperate plea, the wishing stars left are only enough to power the region for the next 10 years, maybe even less. Rose has not made the information on the energy crisis public yet, but perhaps he hints to it at dinner with Sonia and Victor/Gloria, implying that it’s still quite a long ways away. He turns to the legend of the Darkest Day, knowing that that storm is somehow connected to the creation of the wishing stars, and decides to enlist Professor Magnolia to help him research it, as she specializes in the study of the Dynamax phenomenon. That would only result in a meager amount of stars, though, and Rose starts getting desperate. He becomes Chairman of the Galar League as a means to acquire connections with powerful Trainers like Leon, gain access to the Power Spots the stadiums are built on top of, and to collect more wishing stars it’s a minor detail, but there could perhaps be some in-game TV news headline about how challengers’ Dynamax bands will disappear from time to time. Macro Cosmos has had an energy monopoly over the Galar region for decades, and it’s in Rose’s best financial interest to keep it that way, so he scrambles to find a solution.

Really leaning into the businessman side of Rose’s character, let’s say he knows from the start that the Wishing Star supply is running low his company IS the one using them to power the region, after all. Some ideas were pulled from ItsYourPalJacob’s video about rewriting Pokémon Sword and Shield, but I put my own spin on it that I think is pretty distinct.

Star wars autistic screeching