What changed is he's a Washington Post reporter. The Saudis control the Arabian press. Erdogan controls the Turkish press. But the Washington Post's masthead is "Democracy Dies in Darkness" and no matter how badly the Republicans wish it weren't so, they're a minority party in power and Trump himself is widely viewed in the press as a populist puppet of powerful foreign interests. We make much of the Fourth Estate. How much they matter is up to question but how much they think they matter is not. Really, if the Washington Post had chosen to let this slide we probably wouldn't be talking about it. But since the Washington Post started barking about it, all the other dogs are barking about it and suddenly, the Fourth Estate is acting like a political power. I don't think anything changed. I think MBS is a 33-year-old prince with a demonstrated skill at propaganda and intrigue but no tested skill at diplomacy and "murdering a journalist" is a diplomacy test, not a propaganda or intrigue test. I think MBS saw it as an intrigue test because he wanted to send a message to other dissidents ("you are never beyond our reach") but didn't consider that not all the factors of the equation were under his control. The world has been low-level annoyed at Saudi Arabia for decades and irritated at MBS in particular; bringin' a bonesaw to a marriage fight turned out to be the spark the conflagration needed.
I was thinking this was a Turkish power play. Erdogan is an absolute monarch as well so the fact that they are releasing so much footage and data to the media means his interest are in getting this to blow up as much as possible. The coverage this is getting on social media, reddit, etc makes me think that there are a lot of powerful actors at work spreading the outrage for their own purposes. I agree that its an outrageous story but the fact that its being talked about so much in spite of so much Saudi money looking to make it go away makes me wonder if there is some other powerful actor moving behind the curtain. I'm surprised you attribute this to an independent move by the WaPost and the 4th estate. I could see that being the spark, but someone else has provided the fuel and keeps pouring more onto the fire.
I think where we disagree is in how much power Turkey has to play with. They spent half the cold war on the outs with Europe over Cyprus. They're currently trying to figure out if they wanna sidle up to the US or Russia. Erdogan isn't an "absolute monarch" - he's a nominally elected official who has rolled back democracy every chance he gets but he doesn't get to issue edicts the way the Saudis do. As far as Saudi Arabia, they've belonged a lot more to the Republicans than the Democrats (especially since Carter let the Shah in back in '79). Bush-era Saudi Arabia might as well have been a Republican protectorate. Democrats made much of the fact that 15 of 19 9-11 hijackers were Saudi and Michael Moore pointed out in Fahrenheit 911 that the only guys in the sky on September 7 were the bin Laden family and their coterie. As such the Saudis are an excellent bete noire for Democratic foreign policy expression. The Turks basically had to own up to bugging the Saudi embassy, which everybody pretty much knew they did. By letting things trickle out the way they have people are pretty much okay with the Turks bugging embassies. It took 'em a while to get there tho.