-
Let's try the other side of the coin.
Let's say the great powers, including Russia, all just backed off and left Daesh alone. What would you expect to happen?
Depends what you mean by back off. Leave them alone totally or not carry out direct attacks? If you leave them alone totally then either they will succeed and establish a power block, or local groups will fight them for power and absorb them and their supporters into their ranks.
I've heard some interesting arguments and explanations recently for the rise of Islamic extremism. One that has really struck me is that it is rooted in the under representation of the Islamic states on the world stage after the fall of the Ottoman Empire. Tied to that is also the lack of stability caused by the fall of the Ottoman Empire and the West's subsequent medeling.
Linking this to your question... The logic is that you need to stabilise these countries and empower them. This can only be done by the local/regional groups. That then means that a proxy war makes the mors sense than direct action. Ultimately though in this argument you need to allow stronger Islamic states to exist and allow them a voice on the world stage.
Let's try the other side of the coin.
Let's say the great powers, including Russia, all just backed off and left Daesh alone. What would you expect to happen?
Let's also say the west backed off and Russia didn't. What would you expect to happen then?
Edit to add - I'm not expressing an opinion for or against, I just want to know what people think would be the outcome of not intervening.