If the Lord is to come on the earth in the flesh, then what is the meaning of the coming on the clouds?

According to Rev. 17:15, water symbolizes fallen or sinful man. Then what does a cloud mean? Clouds are vaporized water. Regardless of how dirty water may be, when it evaporates into a cloud, it becomes purified. Likewise, clouds signify the men resurrected or reborn from fallen men, or in other words, the resurrected believers reborn from the sinful world. The metaphor that he will come on the clouds means he will come again among the saints that God prepared.