They only done fighting in France in WW1 in the trenches etc. but WW2 was mainly fought in the skies etc.
Ummm ... not exactly, I'm afraid.
Yes, there was a great deal of aerial combat in World War II, both in Europe and in the Pacific, but there was plenty of ground fighting as well. Hitler conquered mainland Europe with a huge army; there was an extensive land battle across North Africa; and of course the Allied invasion of Normandy was the beginning of a tremendous land-based campaign that would end with the Nazi defeat.
Then there's the war at sea, too. The "Battle of the Atlantic" went on unabated for six full years with submarines doing tremendous damage to both merchant and naval vessels. The Pacific war was mostly a Navy war with the British and American fleets trying to defeat the forces of Japan.
The fact that it was a truly global conflict waged in the skies, on land and at sea, and fought on most of the world's continents and oceans, makes it especially interesting to study. There's so many different angles and points to consider. That's why it's so fascinating, as you say, to "learn lots about it".