During the Cold War, socialism was spreading everywhere, including the Middle East. However, the US wanted to exploit the fact that socialism - on the surface - is an “atheistic” ideology. They tried pushing this aspect onto Muslim communities, making it seem like socialism is inherently incompatible with their beliefs, unlike capitalism which doesn’t care about what you believe. This meant the USSR was the biggest enemy because it was the largest socialist nation that was seeking to expand its influence

It was not just about ideology. The Middle East also produces a ton of oil which meant that if the USSR had influence there, they would control the flow of oil thus have a major advantage in war and production. The US spoke to the monarchs and secured a deal: constant oil and globally sold in USD in exchange for American military presence and weapons sales to stop socialism and SA becomes a regional power.

Various ME countries also disliked socialism and would help the US. But SA had the money and local influence to direct covert operations, and now they have every ounce of assistance available with the US.

Basically, the US helps the monarchs stay in control by keeping them happy to side with the US. Their shift towards China and the yuan is interesting. It’s opportunistic and I suspect they’ll go back to the US once they get pressured enough to satisfy SA’s demands. But right now both countries are trying to please the monarch so they continue to be propped up. They’re not phased by China’s hammer and sickle because they know China doesn’t care about regime change in the modern day. They just want the goods. However, the US wants to go scorched earth on anyone who doesn’t agree with them, and SA is wary of that as seen with its refusal to sanction Russia and getting sanctions themselves (thus going to China).