As much as Arthur wanted to save them because it was the right thing to do, and he always wanted to be a hero that saved everyone... everything changed when his big brother was forced to put his life at risk to deal with the Leviathan for their sake.
But, it had to be done since the Leviathan was the only entity capable of absolutely breaking apart his fortress... not the gemstone itself, but it was powerful enough to uplift it from its roots entirely.
Now, he still wanted to save them, but he was just as irritated as Nurah.
Meanwhile, when Arthur emerged from the portal, he found himself falling in midair, but he didn't panic... he scanned the situation from the sky and saw that Shia, Jojo, and Nurah were dropped off at Tyrese's team.
Shia used Bleeding Pillars to manifest a similar sampling-like dome around them, which sealed them with a couple of Corrupted, leaving the majority outside.
'Here she comes.'
