As for why millions of living creatures perished under the fierce wind at the beginning, the reason is not complicated. It was because he was in seclusion at that time, needing to fully immerse himself, hence initially unaware of those visitors from the various realms.
Fortunately, the retreat did not proceed smoothly, so Jiang Hui withdrew early.
Otherwise, it would likely have only been those Immortal Kings and a few Quasi-Immortal Emperors among the visitors from various realms who could have survived to reach the dam.
The reason he aided these visitors from various realms was because he instantly perceived their intentions.
These visitors were seeking a sliver of survival to escape the impending catastrophe. As it happened, he needed fresh blood to supplement the experience points of the Immortal Domain, so the arrival of these visitors was like a ready-made opportunity, and Jiang Hui would not miss this chance.