Other things aside, the Angel race still wanted their pride. If they let the Human race get slaughtered here, the Angel race's reputation among the Myriad races would be wholly destroyed.
That was undoubtedly creating a joke out of the Angel race's reputation. Once their reputation was ruined, it would take an unknown amount of time to recover. The entire race's luck would be damaged.
It was a matter that concerned their race's fate. No matter how much the Angel race disliked the Human race, they wouldn't support it. They would even oppose and stop it.
It wasn't that the Angel race was friendly and valued the Human race. They wouldn't allow anything to happen to the Human race here just for their reputation.
If someone mentioned the Angel race in the future, someone might immediately say it was the race that sat by and watched their allies get hurt. Then the Angel race's reputation would stink.