The disciples in the outer sect were excited and nervous because two special events were taking place at the same time. These two events take place once every five years.
The first event was the outer sect competition, while the second event was the welcoming of new disciples. None of these concerned Arthur, so he didn't care.
The outer sect competition wasn't compulsory for S-grade students, and he didn't care for the reward since he was rich, so he decided to focus on learning how to forge armaments.
The new disciples that will be accepted into the sect will be given a new mountain as their accommodation. So he didn't have to move out of his house to make room for them. This gave him fewer reasons to care.
The event that most people care about is the outer sect fighting competition. After all, it is the event that involves most of the disciples and will decide if they get promoted or demoted.
