The reasons may be varied, and perhaps Russia added alot to the mix with their less discriminating bombing... Add to that better financial tools for tracking and removing illicitly gained moneys from their coffers.

But, really, that's beside the point. The how. The important thing is the what. And that is they are getting financially squeezed.

And their pay scales allow for internal dissent since foreign fighters get paid twice the rate of their locals...

Good to see them make poor decisions.