There is a suggestion in the thread above that Khashoggi was a friend of bin Laden. It appears he was in the 1980s. Khashoggi interviewed bin Laden in in Afghanistan back then, at a time when the CIA was funding bin Laden and other Muhadjadeen, and Al Qaeda didn't exist.
Some info here:
It is natural that the Saudis would claim he has connections with or sympathy for the Muslim Brotherhood. That is their standard criticism of any pro-democratic Muslim. (The main ideological difference between Wahhabism and Salafist/Muslim Brotherhood is that the latter is amenable to democracy; the former is not.)
Khashoggi's disappearance or execution is nothing new, since MBS has become powerful, and even before he became Crown Prince. Eg see the following, for some others kidnapped from Europe:
MBS started the war in Yemen. The worst war on the planet in the last few years, after the Yemenis rejected the president Saudi Arabia wanted in charge. He doesn't even put troops on the ground. He just bombs them from the air, trying to starve them into submission, using US supplied weapons. The long term consequences are likely to be devastating. Yemen, though poor, has a population nearly the size of Saudi Arabia.
Many people might not know there is a significant Shiite minority in Saudi Arabia. MBS has also waged all out war against them, in one location:
Lets not forget MBS kidnapped the Lebanese Prime Minister in Nov last year:
Overall, the Saudi regime under MBS is the new Saddam Hussain or Col Gaddafi. Possibly a lot more dangerous.