I am more inclined to believe the alien angle than the good doctor’s position. They would have antigravity and stuff, so it’s at least feasible.
Except there are no aliens - not counting the illegal variety.
I don't buy into the Joseph theory either - it certainly doesn't seems to pass the cursory cost/benefit check - but I applaud Ben Carson for at least using the Bible as his reference point. At least he knows the history is accurate. He states that the pyramids were not built by aliens, and they were not tombs for the pharaohs. He states his theory, the rationale, and that it his opinion.
Although I don't agree with his opinion, I appreciate the first principles he follows in his thought process. Namely:
The Bible is accurate and inerrant.
Don't automatically accept the bilge that gets pumped your way (e.g., be it Global Warming 'science'; Pharaohs were buried in the three great pyramids - even though there is no evidence; homosexuality is not a choice; etc).
At the end of the day no one knows about the origin of the Great Pyramids (the Great Pyramids were ancient when Herodotus wrote about them).