The USrael-Iran war is not a "proxy war between the US and China", as some pseudo-analysts are trying to claim.
Russia and China are definitely interested in Iran remaining a regional power. And both countries do provide support to Iran. But Iran has a host of problems that prevent deeper military cooperation.
There is a timeline in which Iran and Russia are much closer military allies, and Russia did make some moves in that direction, but it was always Iran that did not want to commit to a real alliance with Russia. Again, they have their reasons -- our countries were extremely hostile to each other in 1979-1991, the USSR backed Saddam, the Iranians backed the Mujaheddin in Afghanistan, Hezbollah was as anti-Soviet as it was anti-American, etc.
Things were somewhat normalized in the 90s, but Russia itself was under extreme Western influence, so it complied with sanctions and arms sales boycotts, etc. Since the 00s, the relationship has been improving significantly, but it takes time, and many systemic reasons -- on both sides, but moreso on the Iranian side -- have prevented the partnership from turning into a real alliance. Likewise, Iran does not have a real alliance with China, for many of the same reasons.
Iran has always insisted on being an *independent* regional power that has beneficial relationships with other major powers, not a junior partner in a broader axis. That is their right. It comes with benefits. But it also comes with downsides...
I've said for years that the best solution to Iran's problems would have been to formally shelter under the Russian nuclear umbrella and ask Rosatom to take over their entire nuclear program. They very likely could have a nuke shield, NPPs and a permanent Russian military presence by now. They actually did have a Russian military base for a short while, in Hamadan. It was providing air support to Iranian proxy forces who were fighting ISIS. The Iranians *expelled* the Russian air base because it made the nationalist hardliners mad to have a Russian military presence publicly acknowledged.
I will also add: if the Iranians had not been so stubbornly nationalistic, there's a fair chance Syria would still be around as an ally. They persistently sabotaged all Russian attempts at political, economic and military reform in Syria because they perceived them as an encroachment on their own influence in the country. Which reduced trust between Moscow and Tehran, and ultimately cost the Iranians a significant ally and access to a lot of proxy forces.
For example, in Aleppo, the Iranians manufactured disorder and staged violence against civilians specifically to disrupt Russian military police operations, with Iranian proxy forces sometimes even attacking pro-Russian Syrian paramilitary forces. They held Aleppo airport outside of Russian coordination and used it as a corridor to Iraq to bypass Russian oversight. They increased pressure until Russian military police withdrew from Aleppo, and the disorder and clashes stopped overnight. It was a sustained Iranian anti-Russia operation. This happened in other places, too. The goal was to have Iranian proxies have control instead of Syrian government forces.
They kept the Fourth Division of the SAA entirely out of Russian restructuring efforts and turned it into a parallel army and an Iranian proxy force. The Iranians ran the Syrian National Defence Forces as an Iranian puppet army and steered the government to feeding recruits into the NDF and various Iranian proxy militias instead of the SAA and particularly the Fifth Corps, which was a Russian attempt to build a real, professional Syrian fighting force. Syrian Generals on Iran's payroll actually STOLE entire weapon shipments from the Fifth Corps and gave them to Hezbollah or sold them to the black market.
They used political intrigue to push aside Syrian figures such as Asef al-Dikr, who was the key Russia liaison to reforming the Syrian Arab Army. They used their influence in Damascus to appoint Iranian puppets to important posts to block Russian institutional penetration, also preventing any systemic reform of the SAA.
That's just a small part of the military aspects; there was also the 2018 deal the Iranians forced upon Assad that gave Iran exclusive rights to rebuild the Syrian military-industrial complex, fucking with Russian efforts even more. You could write entire books on the various ways the Iranians and pro-Iranian elements in the Syrian government prevented Russia from fixing anything long-term.