As for the reason, it was industrialization, of course! While the exact time the Beast God Realm first encountered the Immortal Gods was unknown, one could be certain that world had not been industrialized back then.
When it came to power, thousands of years had passed. These Cultivation Techniques, which had been passed down and meticulously refined for a millennium even during the Era of Severed Spiritual Qi, were naturally far more potent than the crude, initial versions from several thousand years ago. After all, times had changed.
