Why? Who knows, exactly. I believe it's more than oil & big Corporation..$$$ involved. But the proof is so obvious, whether they called it "moderate Islam" on occasions or "radical Islam", both are same deal.
Overall, the above line of policy won't wash much longer. This spread of Islamism is Very dangerous, especially when 'you giveth and you taketh' approach. If we don't want Islamic terrorism, just don't spread or help it. Full Stop/Period.
None of the so-called 'Islamic countries' could have survived as long as they've to spread their Islam without America & its 'coalition' countries helping them.
Don’t worry, FWIW, we could see a bigger offshoot of ISIS down the road, after all, ISIS came after we supposedly killed Al Qaeda by killing bin Laden.