But for this purpose I have raised you up, to show you my power, so that my name may be proclaimed in all the earth. Exodus 9:16 (ESV)
God showing his Sovereign rule and authority, he even uses evil rulers to accomplish his purposes and spread his fame.
This, the first of his signs, Jesus did at Cana in Galilee, and manifested his glory. And his disciples believed in him. John 2:11 (ESV)
Miracles should always point to faith in Jesus