Establishing a kingdom requires long-term planning; it is not something that can be accomplished in a short amount of time. For now, the urgent task is still to plunder Slankus' treasures—everything requires money, and no matter how much there is, it can be spent in an instant.
Slankus' underground lair only resembled a maze but wasn't truly one. Even though Leon wasn't a Minotaur—Minotaurs possess Maze Recall, enabling them to perfectly remember any path they've ever walked—his excellent memory made it easy enough to locate the passageway leading to Slankus' Treasure Vault.
The journey would inevitably be filled with chaotic plant guardians, magic statues, and traps, but all of these had already been handled by Slankus. Such obstacles wouldn't stop Leon, whether he used claw attacks, swung his sword, or resorted to his Samadhi True Fire if necessary; at most, it would waste half an hour to an hour of his time.