It seems like the sticking point was PIF being involved - the Saudi wealth fund - which would mean they're literally owned by the country Saudi Arabia.
This is distinctly different from us being owned privately by Sheikh Mansour throuh his private fund ADUG.
Now we might all know that HHSM might be little more than a figurehead and Khaldoon/the exec council are the real players, but on paper it's Mansour.
I wonder if the Saudi's will come back with a similar private ownership figurehead installed.