Was world War II a continuation of World War 1 and why?

Yes it was. The peace treaty of Versailles in 1919 basically was - in spite of US President Wilson's warnings - an exercise in revenge by France and Britain: unrealistical and gigantic 'damage' payments, giving away large pieces of Germany to newly-established eastern European countries, forcing Germany to fire almost its entire army (and so making it impossible for Germany to control the post-War internal unrest, partly caused by bands of discarded soldiers who had nowhere to go, the so-called Freikorps) and crippling its economic recovery.

These factors all created enormous resentment in Germany and made possible the rise of the Nazi party and Adolf Hitler. His taking back parts of the former German Empire that had been given away - like the Rhineland and Sudetenland - made him very popular in Germany. Even in his invasion of Poland (the cause of WW 2) he was for a large part also "taking back" parts of the former German Empire that had been given away to newly established Poland.

Even back in 1919, economic and military specialists had been warning that the Versailles Treaty would cause the war to be resumed within a few decades.