This proved that the prophet Isaiah was right: God, who believed what we preached? Who recognized God's arm, outstretched and ready to act?
First they wouldn't believe, then they couldn't - again, just as Isaiah said:
Their eyes are blinded, their hearts are hardened, So that they wouldn't see with their eyes and perceive with their hearts, And turn to me, God, so I could heal them.
Isaiah said these things after he got a glimpse of God's cascading brightness that would pour through the Messiah.