After the ascension of Christ our Lord is often said to be sitting down. He is not merely seen slaughtered and dead, but raised again with sacrificial marks upon Him. He stands before the throne of the Father in all the vigor of His eternal life. The resurrection of Christ is not a fiction, but a fact. In the vision John sees that Christ has vacated the throne and the right hand, and He stands ready to take His great power and act.
Standing indicates a readiness for action.
We believe not in a dead Christ only. Our faith does not terminate at the garden tomb. We believe in a resurrected Redeemer, standing in Heaven full of energy. John sees Christ as He stands to take to Himself His rights, purchased by His death on the cross, about to usher in His reign. Christ is about to rid the world of its usurpers and to put down all false authority.