America and Saudi Arabia are working more closely now, although the tensions from the Obama era surely remind the Saudis that they need a powerful friend somewhere. Russia isn't the answer. China is by default. So don't jump to the worrying stage:
The Chinese Vice Premier Zhang Gaoli’s visit to Saudi Arabia in the summer of 2017 was a deal maker. There was agreement on a $20 billion Sino-Saudi investment fund, along with discussions of nuclear energy projects and other economic agreements worth nearly $70 billion.
So what is going on between the two countries? Why is a communist superpower collaborating with an American ally in the Middle East? Is there more to this than economic cooperation? And could it be the start of a power transition in the region, with China taking over US leadership?
China needs oil where America is exporting energy.
China is a potential foe of Russia who supports Syria and Iran--Saudi Arabia's main foreign enemy.
China is willing to sell weapons to anyone (and Saudi Arabia used to have Chinese silo-based ballistic missiles lacking only nuclear warheads) no questions asked.
China has a UN Security Council veto.
And China did move into the neighborhood with a new base in Djibouti at the southern outlet of the Red Sea.
So while Saudi Arabia could muck things up with a full China switch, closer relations with America make that unlikely right now.
And an outreach could strip Iran of an ally; gain weapons sales if America or Europe (especially) balk at selling the Saudis weapons and ammunition; gain a reliable customer invested in Saudi survival; and compel Russia to be the lone veto wielder in defense of Iran, which will help isolate Russia in the Arab world.
A Saudi outreach to China could complement the growing American-Saudi cooperation against Iran.