I think it is about swallowing the less poisonous pill.
Of course, he is related to Dodi Fayed (the dude killed with Diana), and his uncle is Adnan Khashoggi, the billionaire arms dealer. The entire family was very well connected in the West, especially the elite (British monarchy, Washington DC, etc).
But beyond that, he was also a member of the Muslim Brotherhood, a diametrically opposing philosophy to Al Saud's Salafism (but still islamist and regressive, in my opinion. Bin Laden was a member, someone who Jamal was friendly with for a long time).
Perhaps the American media are more closely aligned with MB than with Al Sauds. This would explain the outrage to me. The GCC nations are extremely anti MB. However, MB has a relatively positive presence in the US. Here is an article from WaPo about when CAIR was designated as a terrorist org in UAE due to MB ties (https://www.washingtonpost.com/news/worldviews/wp/2014/11/17...).
I think the US generally turns a blind eye to both MB and Saudi atrocities. However, MB is a little better connected socially in the US (elites, civil rights orgs, etc) compared to Saudi, which is better connected on a federal level (aid, trade, investments).