When the entire world was restless because of the metal giant, the appearance of the rainbow bubble was no doubt adding fuel to the fire, making the already rampant doomsday talk even more popular.
If it was just the metal giant, then it could only be considered a coincidence. But if there were other supernatural phenomena that followed, then it couldn't be explained by a coincidence.
The panic that followed could very likely cause the entire world to fall into chaos!
Therefore, the best way was to completely seal off the news about the rainbow bubble, or complete the exploration before the news spread. Then, use a powerful weapon to destroy it in one go!
Only the courage to cut the Gordian knot could completely control the situation. It was easy to say, but it was very difficult to do.