Marty I see scripture showing that the dragon/satan will inhabit the human body of (The Beast) who gives the human man his power and authority
You will closely note (The Beast) rises out of the (Sea) which represents people, humanity
Beast Rise Up Out Of The Sea, "People"
Revelation 13:1-2KJV
1 And I stood upon the sand of the sea, and saw a beast rise up out of the sea, having seven heads and ten horns, and upon his horns ten crowns, and upon his heads the name of blasphemy.
2 And the beast which I saw was like unto a leopard, and his feet were as the feet of a bear, and his mouth as the mouth of a lion: and the dragon gave him his power, and his seat, and great authority.
Satan is King of the bottomless pit, and rises when the pit is open as seen In Revelation Chapter 9
Revelation 9:11KJV
11 And they had a king over them, which is the angel of the bottomless pit, whose name in the Hebrew tongue is Abaddon, but in the Greek tongue hath his name Apollyon.
But you still haven’t answered the question.
If so then how can the beast also be the 7th and 8th kings?
I’m not sure why you can’t see the beast as being a demonic being influencing kingdoms and possessing their leaders like we see in Daniel chapter 10
Don’t forget that John said that a the beast was “now is not” and also “now is” as a king. He then goes to say that the beast is also the 8th king. Satan was never “now is not”
That’s because the beast is a demon who was locked in the abyss (now is not)and satan released him “now is”.
John also states that the beast was present during his day as the sixth king