Because the current civilization had Talulah, Aibrana, Ling, Nian, Xi, Vina, and others he cared about, while the Previous Civilization basically had nothing to do with him. It was like choosing whom to save when encountering a fire: a complete stranger or a cat that had accompanied you for years. Most people would probably choose the latter.
But one thing was one thing, and another was another.
When he could only save one, Qianyi would naturally save the one important to him first. But if he could save both, why couldn't he choose to have it all?
"Is there really nothing wrong with your brain?" Priestess asked in shock. "Reviving the Previous Civilization won't benefit you in the slightest."
"How do you know the joy of a fish if you are not a fish?" Qianyi did not think it offered him no benefits. An entire civilization's worth of people revived, all of whom liked him—forget forming a band, he could probably even put together a hundred-member orchestra.
"The life information stored within Originium is currently only in a frozen, dormant state, yet it can still develop affection for you. If they awaken and learn that their civilization was saved because of you..." Priestess considered how things would develop, then said, "I'm afraid everyone would choose to awaken in the gender and appearance that best fit your preferences."
To put it simply, if Qianyi liked white-haired, red-eyed beautiful girls, then practically everyone from the Previous Civilization would choose to move toward that aesthetic he liked.
As for what happened afterward, it was very simple.
People of the Previous Civilization: He's so beautiful. I've fallen in love with him, so I want to have a relationship with him.
"If it were just individuals, I would bless you all. But an entire civilization..."