Because they were acutely aware of how terrifying it was to be able to destroy a base and carry off so many secret weapons.
According to conventional logic, such an event was bound to be a planned, organized operation, requiring at least an advanced, highly combat-capable military force; otherwise, it would have been impossible for not a single person at the base to survive.
High-ranking officials in Eagle Country had even begun to grow suspicious of one another.
Chapter 300