Aster applied to be Eldiw's regional Professor to keep the Pokémon Research Lab away from Versil and Victor's hands.
During the main game, Aster runs the Pokémon Research Lab in Hadwarf City in the absence of its founders, his mentors Versil and Victor, and acts as the unofficial Professor of the Eldiw region. Rather curiously, he only makes his position official in the post-game - after defeating Team Dimension, the leaders of which were his aforementioned mentors. Considering how betrayed Aster felt at seeing both Versil and Victor partake in a potentially world-ending ploy, perhaps he had more in mind than just finishing his studies. He might have felt that Versil and Victor were no longer trustworthy enough to run the Lab due to their unethical experiments (see: the X-Gene), and thus vied to keep control of it to prevent them from using his research for further nefarious ends.His nature as a Big Brother Mentor to many of the younger characters, and almost a Parental Substitute to the player character, might also factor in this move. After seeing both Victor and Versil (the player character's own biological father) try to harm the player character, Aster simply doesn't trust them to be near kids. He therefore decided to take the reins to protect the player character, his young assistants and future starting Trainers from his disgraced mentors, especially considering that neither Versil nor Victor have yet faced comeuppance for their crimes. And Luxflon help them if they're up to no good again, because after all, Aster is still the former Lumen and still has Suicune as his companion.
