Luther is the leader of The Umbrella Academy of adopted siblings with superpowers. The man who formed the Academy, Sir Reginald Hargreeves (Colm Feore), never seems to have the best interest of children at heart.
Based on Luther’s multi-year stint on the moon, in addition to Reginald’s interest as stated in season 2 of The Umbrella Academy, it’s highly plausible that the mission was not a complete waste of time.
Reginald knew about the impending apocalypse, so he commits suicide as a way to rejoin The Umbrella Academy. It is not a coincidence that Vanya’s destruction centers are located in the same place where Luther was sent.
Luther from The Umbrella Academy ended up thinking that the mission was just a way to keep him busy away from his home planet, but it seems Reginald might have been aware of something else.
Viewers now know that Reginald is not human, but some kind of alien species. His interest in the dark side of the moon could be related to his true identity, which he kills to protect at The Umbrella Academy.
Reginald is a mysterious man and he certainly has his secrets. Obviously, there is more to the Reginald and Luther story. It wouldn’t be surprising to learn about Luther’s past mission and investigation with The Umbrella Academy season 3.