The dictatorial regime in Syria controlled by a minority Alawite ethnicity minority in that state, appears to have used a variety of tactics widely to be considered war crimes, such as the use of chemical weapons, the use of its Air Force to bomb its own people, shutting off rebels from humanitarian aid, and more, to defeat an armed Arab Spring uprising of its people against decades of dictatorial, one party regime rule there.
There are pockets of dissent, but the Western powers that have the ability to intervene in favor of the rebels (or at least did at decisive moments that have since passed), were unwilling to commit to doing so in the way that they had in Libya just months before the Syrian uprising was in full swing, even after obtaining clear evidence that the regime used chemical weapons against its own citizens, and even has the death toll has approached or exceeded 100,000 in a country with a population smaller than California. The West has supplied arms in a manner that is barely covert, but did not create a no fly zone that could have interrupted Syrian air strikes against its own people, has not instituted a naval blockade, and has not deployed troops or carried out strikes on regime targets with cruise missiles or smart bombs as it did, for example, at the turning point of the Afghan civil war.
In many ways the Alawites, were well suited to be successors to the French colonial rulers of the region. Their worldview was more tolerant and more comfortable with the notion of a secular, multi-ethnic state than the urban majority of more conventional Sunni Muslims, yet as self-described Muslims in a state where the vast majority of the people were Muslims of some description, they were more tolerable rulers than Orthodox or Maronite Christians, and were not committed to isolation from the large world in the way that the Druze minority. Their tribal and clan organization and solidification of a tight ethnic minority community gave them the organizational capability and levels of interpersonal trust needed to seize and hold onto power.
Their mystical and syncretistic brand of Islam, following impulses within the faith not unlike those of Alevis in Turkey (many of whom are also Kurdish), and the Sufi mystical movement within Islam that has thrived in Pakistan, is hardly the secular, Enlightenment outlook that fueled the French Revolution. But, it is also a movement within Islam that provides relief from the intensely patriarchy, harsh and violent discipline, and emotionally restrained Islam of the Wahabbi Sunni Islam promoted by Saudi Arabia.
The Ba'athist party in Syria, like the one in Iraq, allowed a multi-ethnic state with a meaningful and thriving commercial middle class developed a power base separate from the nation's oil wealth that endured for decades, but only at the cost of denying the public genuine democratic elections, political liberties, and freedom of authoritarian abuses of individuals (particular political dissenters).
When the U.S. led invasion of Iraq (based to a great extent on an absurd claimed relationship between Iraq and the 9-11 terrorist) removed Saddam Hussein in Iraq, many Ba'athist went into exile in Syria whose sister Ba'athist regime had not yet fallen. Iraq's long bloody counterinsurgency against Western occupiers and parallel ethnic civil war (that is still far from over and produces major military engagements and terrorist incidents years after the U.S. withdrawal) has turned a multi-ethnic nation with a substantial commercial middle class into a set of ethnically segregated microstates sharing a single stream of oil revenues dispersed by a deadlocked parliamentary system that requires ethnic consensus for many actions. Many influential Ba'athists in Iraq have been disposessed of their wealth and political power. Ba'athist Alawites in Syria and their allies of once influential Iraqis in exile understandably had an intense personal stake in not seeing that scenario repeat itself in Syria.
The U.S. and its Western allies have been reluctant to fully commit to support insurgents, because while they are Arab Spring revolutionaries who are victims of war crimes and want democratic reforms that a socialist dictatorship has denied them for decades, they are also mostly Sunni Muslims looking for an Islamist state who have welcomed assistance of Al-Qaeda and other organizations the U.S. saw as their terrorist opponents in Iraq (a nation which has a Shi'ite majority and many dissenting ethnic minority Kurds, but had a minority Sunni Arab dominated leadership under the Ba'athist regime). The French, who as a former colonial power there would have been a natural to lead a European intervention, instead decided that their intervention against Islamic insurgents in Mali was all of the colonial might that they could manage to exert in the world at that historical moment.
Meanwhile, Russia chose to use its Security Council seat, resurgent naval power, and diplomatic resources to back the old Syrian regime against the Islamist Arab Spring insurgents who seem very similar to the Islamist insurgents in Chechnya that the Russian regime has devoted so many resources to putting down in the interest of showing political control over its territory even if the locals don't want them there. Also, as much as anything, Russia was loathe, as it has long been since the Soviet era, to thwart international efforts to impose global standard in the conduct of sovereign nation's internal affairs, so its natural instinct was to block foreign intervention in Syria as well. Their support for the Syrian regime effectively extended the Russian sphere of influence that had collapsed briefly with the fall of the Soviet Union, without committing much in the way of blood or treasure.
Also, assuming that Syria's old regime does eventually manage to consolidate power, it will have no choice but seek Russian support in international political and economic affairs. Syria has no other patrons. Even the Arab states have turned their backs on the Syrians (since the Sunni insurgents in Syria have more ethnically and religiously in common with them). Russia's small favor will be an expensive one for Syria to repay, perhaps, for example, in favorable oil and gas deals, trade preferences, military procurement decisions, and international support for its controversial actions like its annexation of Crimea. So long as Syria has oil, it can repay those debts, even if its once cosmopolitan, commercial middle class economy apart from its oil wealth collapses for decades as a result of its civil war.