Generally, WW1 was a slow war, with well-thought tactics, however, WW2 was completely different. The Third Reich used the following possible factors as a reason to use the blitzkrieg strategy:
1) Alsace and Lorraine: As part of the Versailles Treaty at the end of WW2, Alsace and Lorraine was given to France. Germany wanted this region, and launched this tactic because France had heavily guarded this region
2) Czechoslovakia: Same reason as above
3) Russia and England: Both countries were known to be slow to mobilize, and Germany used their weakness to take great military action