Bullshit. Iran has been backing Assad forever and they even sent their proxy terrorists in hezbollah and their own revolutionary guard to fight.
The US is now backing Assad, does that put Iran and the US as allies now?
People in Saudi Arabia have been the major backers of the Sunni rebels. Yes, Russia has been indiscriminately bombing civilian areas, especially targeting hospitals But is is essentially an Iran/Saudi Arabia conflict for regional dominance. And you are fucking nuts in your claim that Israel is to blame for the Syrian civil war.
The Syrian conflict with half a million dead, at least 100,000 civilians and 12 million refugees or internally displaced and Yemen has 15,000 dead, mostly civilians with 3 million displaced. Only a fanatical clown would claim Israel is worse than those. Then we can easily look at the internal human rights abuses in both Iran and Saudi Arabia that have led them to be ranked abysmally with respect to human rights.
The Syrian conflict is morally messy, you can't say anyone involved there is clean or someone you really want to back. That's a big problem. So is assigning guilt and blame for what started out as a revolt from farmers after climate change influence drought killed their livelihoods. Assad was a despot, but a minor one, not on the scale of Saddam. Syria was a functioning country that trended towards police state, but it wasn't the worst place on the planet. The civil strife turned into a big clusterfuck with Russia, Turkey, Kurds, ISIS, AQ, Lebanon, Israel, the US and yes, Iran all involved. Iran supported Hezbollah but they weren't the biggest players there.
Why its generally left out of debates is that its such a fucking mess that nobody can figure out who to blame or who's winning or morally what the heck is going on.
Israel, on the other hand, is pretty clear.
You've got a colonial state that's imposed apartheid on the native population, illegally occupied another country and attempted ethnic cleansing for which there are 5 million refugees still waiting, including those poor Palestinian refugees who were stuck in camps in war torn Syria.
So yes, Israel is a much easier subject because unless your a closet zionist/colonialist/racist, its pretty clear morally.