There’s Russia who wants first of all stop terrorists, you know they look for support among russian muslims and we find ISIS groups here and there in our country and in neighbouring ones.
Maybe this is Russia’s primary aim.
I have read that one of the underlying US/UK aims in Syria is to get a gas pipeline constructed from Qatar to Europe. The theory is that Assad would not permit the construction of this pipeline across Syria which is the only viable route, hence the war. I’m not really in a position to judge the accuracy of this claim, but it it is clear from all the skulduggery and politics surrounding Nordstream 2 that natural gas is a resource of strategic, geopolitical import. Therefore this explanation seems at least plausible.
And if this explanation were the correct one, then it provides Russia with another goal which may well supercede that of stopping terrorists – the goal of preventing the construction of this pipeline which would allow the US/UK/Saudi alliance to challenge Russia’s European gas buisness.