I found this comment to be insightful
But the House of Saud always had an almost literal killer counterargument, that they were probably better than any regime that would replace them. Often the world of foreign policy gives you no good options, just lots of variously bad ones. Accepting the Saudis’ help where they offered, and trying to gently nudge them into becoming slightly less brutal and slightly less bad on women’s and minority rights, was probably the safest option.
He then goes on to list multiple articles that, prior to this assassination, lauded Mohammed bin Salman (the leader of Saudi Arabia) as a great reformer and a modern leader.
The catch here is the same as it was in Iraq: you might not like the current regime, but at least they'll work with you in most cases. And there have been some minor successes in "Westernizing" the country, such as women now being allowed to drive as of this year, even if victories like this are still really minor overall. And remember that Al-Qaeda was birthed in Saudi Arabia, with some Saudis still possibly funding terrorism (such as ISIS) as a way to spread Islam. The only upshot there is that government itself does not fund terrorism and frowns upon those who do.
It's unlikely the Saudis will get away from this without some repercussions, however. While they had acted with impunity before, the political pressure to do something (especially in the US) has grown considerably, and in a bipartisan way. Khashoggi had plentiful Western ties and there is now too much scrutiny. Indeed, journalists are continuing to investigate, with sources explaining what happened. While they may not end in sanctions, it would be both embarrassing and damaging to the Saudis to admit they used a diplomatic consulate to commit a murder. At the very least, Turkey may deny the Saudis a consulate, given how there appears to be a continuing attempt at cover-up and the Saudi consul fled the country. Remember, Saudi Arabia is currently leading a coalition against Qatar. While that doesn't include Turkey, it could be a way for some countries to express their distrust, especially if prodded by the US.