Large German units started surrendering to small Allied forces. Yes, tanks and the U.S. arrival helped clinch everything. But the meltdown inside Germany was quite amazing. Think of the U.S.'s final decision in 1973-75 to get out of Vietnam no matter what. And then multiply that breakdown of the warrior mentality by 100.
The Kaiser lost control of his country in the war's final weeks, and the German authorities naively hoped that they would get an OK armistice/settlement if they called it quits. When they didn't, that created such deep German resentment over the next 20 years that a resumption of the war became inevitable.
Bismarck predicted:
"Jena came twenty years after the death of Frederick the Great; the crash will come twenty years after my departure if things go on like this"
"One day the great European War will come out of some damned foolish thing in the Balkans".
http://en.wikipedia.org/wiki/Otto_von_Bismarck#Forced_to_res...
The real lesson from tanks is the impression on the German psyche which led to Manstein, Guderian and Rommel, the concept of Blitzkreig and the fall of France in 1940. Post war tank warfare on the allied side was (generally) very staid comapred to German thinking. Though there were some good thinkers, included Liddell-Hart who showed you could take tanks through the Ardennes...
WW1 ended because Germany exhausted herself utterly in the failed Spring offensive of 1918. The UK's blockade of Germany was having horrific consequences on the home front. Meanwhile the advances that were made in Spring 1918 by Germans led to them capturing lots of supplies from the newly entered USA, thus undermining their morale further.
He was an idiot. There is no such thing as "Blitzkrieg", just dumb luck and huge mistakes on the French's part.
Pershing being a West Pointer, noted that there was no decisive victory on land in WWI and that it would be resumed in a generation. Remarkable prediction.
Aside from cursory school classes and then some reading, I've never really looked into it in great detail.
The elementary school version is "tanks broke the stalemate, and the US/UK rolled through to victory", but it was a lot more nuanced than that, with internal revolutions in multiple countries. WW1 clearly could have kept going for some extended period longer than it did.