Is it because it's a stupid idea? I didn't watch the video because it's 44mins and it's just a stupid idea right off the top.
Do you know what isn't a stupid idea? A circle. Same plans, same god awful location, just make a big circle and double function the thing as a particle accelerator.
tl;dw - MBS murders anyone who opposes him, so no one will tell him it's a bad idea (Jamal Khashoggi voiced opposition to the plan).
Also, it's a bit of a stunt to attract tourists (compared to something like the Burj Khalifa) and has a bunch of promises that are just patently not viable, as opposed to an actually thought out project.
~24m into the video, the proposal for a circle is dropped in as a better alternative (albeit still crazy)
So they actually thought of doing a circle? OMG! My sides!
If there was a god, you know he purposely gave the dumbest people in the world the most amount of money for his own amusement. While I am sure there are some brilliant engineers working on this project, you know damn well what they are thinking.