Although Ronan spoke with confidence, as if finding the Minotaur's treasure would be as easy as retrieving something from a pocket.
In reality, being in an endless labyrinth that changes from time to time, even with a maze map, finding something whose exact location is uncertain is still not an easy task.
Especially after losing the Space Key, the ability to "freely traverse" the maze.
This requires a massive amount of brainpower for analysis and deduction, enough patience, precise control... and some luck.
Moreover, although his "obstacle clearing" plan is going fairly smoothly, it doesn't mean there are no dangers left in this maze.
It's like a piece of fresh meat falling into a trap; he only dealt with that small group of the most troublesome, fierce predators who were the first to smell the blood.
There are certainly other "monsters" in the Minotaur's labyrinth, but their level of danger is relatively smaller.
