Dear lord, do you know what the word allied means? In what universe is Russia allied to any of those? There's a sketchy case to be made that Russia and Iran have an alliance in Syria but that's about it. Russia just finished removing sanctions from Turkey, and has a decent relationship with Egypt based mainly on strategic trade. Nothing even close to an alliance.
Alliance is maybe too strong a word, but they have common interests in different ways. Erdogan of turkey obviously is not interested in working together with the West. No ambition to join the EU anymore, and the demand to have Gulen extradited from the US, which won't happen, will be used as a pretext for cutting ties with the US too. There's a deal to make with Russia and Iran to stabilize Syria, to have the Kurds exterminated and dividing Caucasus between them. Egypt's military regime, inviting Russia for military exercises, is now in trade conflict with Saudi Arabia and being the most populous country of the Arab is interested in taking over the lead of the Arab League. The conflict might be limited to Iran occupying Saudi Arabia's Persian Gulf coast, where the oil and the shia arabs are. The UAE has too much international commercial interests involved, a war there could escalate.
What's this now? Where has Saudi lost the US?
Have you heard of that guy, now what's his name, oh yeah: Donald J Trump?
Except for the Gulf Petro states which are very friendly with the US, Turkey, which is in NATO, and Israel which is one of the most powerful military forces in the Middle East.
Newsflash! Anothjer guy you've never heard of, Erdogan, has turned Turkey into a islamistic tyranny. Still member of NATO on paper, but that doesn't stop them from waging war. A few decades ago they even waged war against Greece, also a NATO member. I don't think they will be active in a war on Saudi Arabia, but they will quietly let it happen and not stop Russian shipping from the Black Sea for example. What has Israel got to do with this? They have stayed out of direct conflict during this "Arab spring" and do well to continue so.
Taking it with what? Again. Look at the geography. Look at the effort it takes for the VMF and VVS to keep a ~5000 man force in Syria.
Saudi's east coast is near Iran, they are certainly capable of marching their huge army into it.
Again, those relationships don't exist. Never mind the fact that Russia simply can't deploy sufficient forces.
Those relationships may very well exist under the table. Defeating the corrupt and incompetent Saudi forces might turn out to be very easy.
I cannot think of any single item I can buy in a shop in Sweden which has been manufactured in Russia, a neighboring country. They export raw materials and weapons. Russia has been totally dependent on oil exports for a hundred years. The OPEC oil crisis of the 1970s boosted Soviet power enormously, low oil prices crushed Gorbachev, high oil prices has been a blessing for Putin. He needs high oil prices again and he needs it soon. He seems even personally very interested in making money from the oil industry.
This is not an exotic scenario. Iraq suddenly invaded Kuwait, remember? This is the same idea. Iran just needs the backing of Russia air force and nuclear protection. Air strikes from Egypt would put Saudi in a three front war including Yemen. That's why the Russian Atlantic navy is now stationed in Eastern Mediterranean. Or what do you think they are up to?