Dunno if the ancient Egyptians could have built it, but I just wanted to point out that, AFAIK, Egyptian obelisks were all monolithic blocks of stone. Moving them and setting them up in Rome, London, and even New York without breaking them posed some significant engineering challenges centuries later. I’ve got a book at home devoted to it – Moving the Obelisks
If you look closely at the ancient Greek columns in their temples and other buildings, they tend to have small chunks missing where a drum meets the one below. When the Greeks built these columns, they stacked the drums one on top of the other, then chipped a sideways H-shaped hole, filled it with molten lead to form a clamp, then prettied it with a plaster finish. When law and order broke down, people came along and chipped the lead out to sell.
You can go to Aswan and see Hapshetsut’s column. She was going to put up the biggest, best bigly obelisk, like the world has never seen. As they were carving out of the granite rock, it cracked. So they modified plans, working around the crack to make it smaller. it cracked again. They walked away from it.
AFAIK, all those obelisks from those days are solid rock. I would imagine the engineering to plant a giant obelisk upright are trivial compared to the engineering challenges of putting a giant narrow chunk of granite on top of several others, in the days before big cranes.
There’s an unfinished column in Luxor temple, indicating that what the Egyptians apparently did was stack smaller columns of blocks and then to get the fancy capitals, they carved the top block once it was in place. No need to handle and maybe damage any fine carving for stacking.
OTOH, you can see in Pompei, they Romans took the easy way. They often built columns from plain red bricks, then covered the outside with plaster shaped to look like those fine carved Greek marble columns.