Then Russia came in and essentially stopped us from entering war with Syria through diplomacy and made Obama look really stupid.
This is a very ... odd ... interpretation of events.
The short version: ISIS believes that they are building the next Third Reich in Caliphate form, as foretold in their mythology. The central component of this belief is the prophecy that the Final Battle will be waged in a very specific location, against a very specific enemy. Their victory in this battle will be the sign that the prophecy has come true, and Muslims worldwide will flock to them to live in the new Caliphate.
The location? Mosul. (Roughly.)
The enemy? Christians.
So what ISIS did was wage a ridiculous one-front war where they drove headlong towards Mosul, leaving their flank completely uncovered, until they got to Mosul, and then dug in.
They then began a terror campaign of ever-escalating horrors to try and bait the "Christians" (aka Not ISIS) into coming into Mosul and starting their glorious Final Battle.
We (the US and our Allies) talked about this a lot, and decided not to fall for the bait. A door-to-door war in a city full of civilians only has one result: nobody wins.
So ISIS beheaded people. Then more people.
Then they started setting people on fire in the public squares. And throwing them off buildings.
And waging a MASSIVE and effective social media campaign to get people worked up, and push their (christian) governments to action.
We didn't take the bait.
We had them completely surrounded, starving without supplies, their supply lines and sources of income (oil fields) cut off, and we settled down for a long siege like people hadn't seen since Sarajevo.
Then dipshit Vlad Putin comes riding in on his white horse and fucked it all up.
He gave ISIS exactly what they wanted: a war on their own territory and terms.
Now every single fighter to die in Mosul is a hero of the Caliphate, a Martyr, and a champion to be celebrated in the great battle against the Christian aggressors. New ISIS recruits flock in every day to die as heroes and enshrine their family name in history. Proud images of the dead fighters and their names are traded like baseball cards amongst the young, disaffected, unemployed, radicalized Muslim youth who see no other future for themselves, so they die for their families.
THAT is why we didn't put boots on the ground.
And THAT is why Putin has ensured this will be the next Afghanistan, because there is no winning strategy when you fight radicalism - a belief system - with bullets. The only way to beat a radical is to have them renounce their beliefs....
... which they would have after another month of having to eat their belts and shoes, walled up inside Mosul, before Putin came in and fucked it all up and turned it into his favorite thing to lose: A ground war.
So yeah... "made Obama look really stupid" shows a fantastically ill-informed view of the situation. The only one that looked stupid - and continues to do so to this day, in Syria - is Putin.