Why can Satan interact with Jesus spiritually even though Jesus is in the flesh?
Jesus and Satan are both spiritual beings. Although Christ was present in the flesh, He was also present in the spiritual realm, so Satan could interact with Him spiritually and show Him all the kingdoms of the world across human history.
Les explains that Jesus and Satan are both spiritual, even though Christ is here in the flesh, He is also here in the spiritual. From that spiritual concept, Satan could let Jesus look back to Nebuchadnezzar, maybe even all the way back to David's great kingdom, and show him forward to all the great empires that would yet come down through human history. Satan then says that if Jesus will fall down and worship him, He can have control over all these nations. Les notes this was quite a temptation, and Satan must not have known that these same nations will one day be under Christ's rulership when He rules and reigns, coming as a result of His sovereignty.