They lacked the spiritual insight to recognize Him as the Messiah, the Son of God. The Bible does not record that Christ marveled at the miracles He wrought. When He healed the man born blind, when He raised Lazarus from the dead, these seemed to Him to be the most natural thing to expect. We ourselves marvel when we see miracles of body healing, a restoration to physical health. We tend to be more impressed by these external manifestations than by the spiritual restoration of a diseased mind and sinful spirit.
People are far more impressed by outward wonders.
He marveled at people's lack of faith. What we marvel at is an indication of the kind of person we are. We stand overwhelmed by the tragedies of life. But our great need is the miracle of spiritual rebirth and transformation. Not the loss of property, health, money, or position is our greatest concern.