This is just so lazy. Yes many of the 9/11 guys were Saudi citizens, but you can’t draw straight lines between that and the Saudi government. Toppling the house of Saud is an explicit goal of Al Qaeda. It’s like suggesting Snowden is clearly acting on behalf of the US government because, duh, he’s a US citizen.
As for people in power making the Khashoggi case a big deal, that would be the Turkish government. They have many reasons for disliking the Saudi leadership, so many I won’t even try.
‘Donors in Saudi Arabia’ isn’t the same thing as the Saudi government. They are very sloppy with their money though, hence the reference to secondary funding (not a direct line) of groups including Al Qaeda, but that’s more like Al Qaeda supporters embezzling Saudi aid money that intentional support by the house of Saud for a group that hates them and that attacked a city the Saudi royal family has invested billions of dollars in.
The problem with the Saudis is they are very sloppy with their money, pretty incompetent and see certain forms if jihadism as legitimate. The incompetence means they often act counterproductively. Those are all problems and the western world needs to try to manage and limit the damage they cause. However hallucinating conspiracy crap on top of that just obscures the picture and makes tackling the real problems a lot more difficult.
And the taliban didn't finance or plan the attack on the US, they merely wouldn't give up those who did. Even if the Saudi government isn't directly financing salafist or wahhabist terrorism (and it's not clear that they aren't [1]), they certainly aren't doing anything meaningful to stop the massive amount of it that is coming out of their borders or out of the madrasas they've been funding all over the world. Afghanistan never had a strong diplomatic/business relationship with the US, so they get the hammer at the slightest malfeasance. As I said before, the diplomatic/business relationship with SA is more important than American lives.
These terrorists are upset about the same thing you are, the ties that essentially make Saudi Arabia a vassal state. Cracking down on them only strengthens those ties, fostering more anger.
As for people in power making the Khashoggi case a big deal, that would be the Turkish government. They have many reasons for disliking the Saudi leadership, so many I won’t even try.