>>47850222It's because it won't happen for a thousand years that people (including Leon) kept putting off helping him, and he was worried that future generations will keep doing the same thing until it's too late. It was established that Leon previously declined to help Rose because Rose claimed that they had discussed it multiple times already. As a result, Rose probably didn't believe Leon when he said that he would help Rose after the tournament. Since Rose knew he'd need the help of someone strong to tame the legendary Pokémon, he felt he had no choice but to force Leon into helping my publicly broadcasting that Eternatus has already been awoken and needs to be stopped.
I'm not saying it's well-written, just explaining how the game presents it. In the game's defense, it doesn't hide that Rose is supposed to be kind of crazy. He probably got obsessed with being seen as the guy who solved the energy crisis and got carried away
