The Trinity concept does not believe that Jesus kept His word to come again in the generation of His contemporaries (Matthew 24:34, and elsewhere). However, Jesus did keep His promise, and thus He is filling the heavens and the earth and not still restricted to the right hand of God.
Because those who formulated the Trinity doctrine did not believe in Jesus’ accomplished Second Coming, they have God stuck in a state of suspended animation whereby Jesus has not yet come to judge the living and the dead. If Jesus is not yet Judge of heaven and earth, then not only is His word unreliable, but no one has gone to heaven, the dead are still in Sheol below, Satan and his host still occupy places of authority in heaven.
Fear not, however, for Jesus did keep His promise, the dead live in heaven, Satan has been cast down to earth, and Jesus reigns over all of His enemies.
There is no need to doubt the word of Christ.
To learn more about Christ versus the Trinity, see: