"What If":
If the Dark Giant's drowsiness wasn't so profound, and his consciousness could be more alert to discover properly...
If the Dark Giant's time wasn't so urgent, giving him more time to ponder in detail...
Then, he would have noticed that there were quite a few issues with this instance of 'Tyrannical Song + White proving their Dao'!
—Why, when the Heavenly Dao was about to step down, were all the immortals from the myriad practitioners in the universe gathered together?
—With so many immortals present, why did not a single one step forward to stop Tyrannical Song? No one could delay Tyrannical Song even for a moment. He was allowed to start proving his Dao the instant the Heavenly Dao abdicated?
—Moreover, having so many immortals converge in one place seemed like prep work for Tyrannical Song to 'cut through the chaos with a swift stroke,' stunning the audience in one breath, and rapidly proving his Dao!