Arthur only stayed briefly before leaving. After all, he didn't want to go to the party in the first place because he didn't think that the party was important to him.
Whether it was the successful advancement of the four of them or the failure of the four of them, none of them was important to him, so he didn't care about the party.
The main reason he showed up at the party was to show his face and to see the nascent soul pill up close. After showing everyone that he attended the party and satisfying his curiosity about what the nascent soul pill appears like, he left the party.
He left to continue cultivating with heavenly lightning. And when he got bored or too tired doing that, he rested by learning how to make a superior logic unit.
Cultivation had become more difficult since he advanced to the fourth transformation, but thanks to the daily baptism of heavenly lightning, he was able to experience progress in his cultivation every day.
