Why didn't the twelve fully understand who Jesus was?
The twelve did not fully understand His identity because they had not yet comprehended the scope of His power. Though they witnessed Him calm the storm by His word, walk on water, and control fish, they struggled to grasp that even wind and nature obeyed Him as the Son of God with power.
Les explains that even after Jesus spoke the Word and the wind died down and the sea became calm, the twelve still did not have full comprehension of who He was. They asked, “What manner of man is this that even the wind obeys His voice?” They could not yet comprehend that He could speak a word and the wind would die down. He also manifested His power over nature by walking on the water; Peter tried it and began to sink as soon as he took his eyes off Jesus. Other signs included knowing about the tax money in a fish’s mouth, and in the last chapter of John’s Gospel, directing the eleven to put their net on the other side of the boat after catching nothing all night, resulting in a full catch without the net breaking. Paul refers to Him as the Son of God after the seed of David, but with power.