Jesus' awestruck disciples receive newfound understanding of the power and glory of their Lord and Master. His power definitely impresses them, but His faithfulness, peace, and the rest of the fruit of the Spirit (Galatians 5:22-23) are what truly awed them. This miracle brings them in reverence, wonder, and godly fear before Him. Christ shows that the power of the earthly elements is dwarfed by the mighty word of the Lord, and it stirs them deeply.
This reveals what the full measure of God's Spirit can accomplish through a faithful human being. Jesus explains to His disciples in Mark 11:23-24:
For assuredly, I say to you, whoever says to this mountain, "Be removed and be cast into the sea," and does not doubt in his heart, but believes that those things he says will be done, he will have whatever he says. Therefore I say to you, whatever things you ask when you pray, believe that you receive them, and you will have them.