The roots of the relationship goes back several decades.
By the late 1970s, the state apparatus of the Baath regime under Assad had consolidated into an anti-Sunni orientation. Official propaganda incited Alawite farmers against rich Sunni landowners and regularly disseminated stereotypes of Sunni merchants and industrialists, casting them as enemies of nationalisation and socialist revolution. Bitterness towards the Assadist regime and the Alawite elite in the Baath and armed forces became widespread amongst the Sunni majority, laying the beginnings of an Islamic resistance. Prominent leaders of Muslim Brotherhood like Issam al-Attar were imprisoned and exiled. A coalition of the traditional Syrian Sunni ulema, Muslim Brotherhood revolutionaries and Islamist activists formed the Syrian Islamic Front in 1980 with objective of overthrowing Assad through Jihad and establishing an Islamic state. In the same year, Hafez officially supported Iran in its war with Iraq and controversially began importing Iranian fighters and terror groups into Lebanon and Syria. This led to rising social tensions within the country which eventually became a full-fledged rebellion in 1982; led by the Islamic Front. The regime responded by slaughtering the Sunni inhabitants in Hama and Aleppo and bombarding numerous mosques, killing around 20,000–40,000 civilians. The uprising was brutally crushed and Assad regarded the Muslim Brethren as demolished.
You'd expect party unity between Syrian Ba'ath and Iraqi Ba'ath, but Saadam was labeled a fascist and the Syrian regional branch recognized Khomeni rather early on. Survival and having regional friends were more important than playing games.
Again, the Ba'ath party is 100% secular. Secularism is a cornerstone of their party. It has nothing to do with Sunni and Shi'a here, it has to do with a theocratic regime in a partnership with exactly the opposite.
Of course by international law they shouldn't be doing that.
But can you really blame them? Where is the international law that protects the people from a dictator? And prevent outside interference to keep that dictator in power?
If international law doesn't protect the people against oppression, then the people has little use for international law. And they definitely don't need an outside influence that support their oppressor.
For the same reason USA shouldn't have held such a grudge against Iran for their attack of the US embassy during the rebellion in Iran.
Unfortunately the ship has sailed on that one. And Iran is now a Russian ally.
Of course by international law they shouldn’t be doing that.
International law is a product of, and supported by, nation states. If the previously ruling government has fallen, it effectively doesn't have a nation that respects the binding of international law. When a new government forms, that government will most likely take up the mantle of support for international law in exchange for international recognition. Right now on the ground its a bit of a free-for-all, I'd imagine.
To be fair USA did sabotage Iranian democracy until it collapsed under American lies and Propaganda designed specifically for that, and then they instated a dictator.
But Iran has clearly gotten worse which was to be expected with a theocracy.
Tell me you have no concept of centering Syrians in an analysis of the situation in Syria without telling me you have no concept of centering Syrians in an analysis of the situation in Syria.