Why was the zeppelin needed?

Answer 1

In peaceable and military aviation, the zeppelin was an important step forward. In the early 1900's, airplanes were powered box kites which could carry a pilot and maybe one passenger (or observer for military purposes). Zeppelins could carry more passengers, or bombs. They could also fly higher and for longer distances, and they were less affected by weather. Unfortunately for the zeppelin, technology allowed the airplane to surpass it in the 1930's, and zeppelins have not been seen again.

Answer 2

Heavier-than-air technology had not yet progressed enough for airplanes to travel long distances by air with heavy weight (cargo, passengers.....and in war, bombs). As the 1920's approached this situation was changing rapidly, with more powerful engines and stronger airframes, but the zeppelin could still stay in the air longer and carry more weight than an airplane into the 1930's.