The diametrically opposed goals of Russia and the U.S. in Syria
In Syria, the goals of the United States and the goals of Russia are diametrically opposed.
The United States is not in Syria in order to combat ISIS, because ISIS is a tool used by Obama's administration to overthrow Bashar Al-Assad.
Therefore, the Russians have blocked the use of the tool for that purpose and this has made the situation in Syria a confrontation between the Russians and the United States.
So, their interests are diametrically opposed and there was no chance of any kind of agreement. Yes, Russia was trying to use diplomacy, but the American side was unwilling to publicly recognize that the United States' intention is to get rid of Assad.
In a wider context, the oligarchs who’ve ruled the United States for so many years are disturbed with Donald Trump. They know that Donald Trump said that he sees no point in conflict with Russia.
Therefore, the oligarchs are still trying to create a war situation so that Trump would be already captured by the momentum towards war and couldn't block the goals of the neoconservatives and the oligarchs who benefit through war. This is an orchestration of a clash.
Syria is a war stage. If there will be a serious conflict between Russia and the United States, Trump can't do anything about it.
This is a very dangerous situation. It comes out of the American neoconservative drive for hegemony over the world. The neoconservatives regard Russia and China as checks on the ability of the United States to act unilaterally, and are for trying to get rid of Russia and China as constraints of the American power.
This is a problem that confronts the whole world. The Europeans are American vassal states and so Russia has not been successful in trying to wake up the Europeans to this danger, until now