God is sovereign over governments, but they are often evil. When they are, God's people demonstrate allegiance to Him by refusing to obey, knowing full well that they may face temporal consequences.
The tension that has been building since Joseph's brothers first came to Egypt is released as he reveals who he is! They are frightened, but need not be: Joseph sees God's sovereign hand at work, preserving a nation, and restoring a family. This is what God can do!