Why were tanks no good in World War 1?

Answer 1

The main problem with WWI tanks was mechanical reliability. The internal combustion gasoline engine had only been around for twenty or thirty years, and were not yet very powerful or reliable. In attacks, most tanks were stopped by mechanical breakdowns, rather than enemy action.

Where tanks did manage to crawl, slowly, up to enemy positions they were very effective, as there were not hand-held antitank weapons available for front-line infantrymen. The appearance of tanks rumbling forward would often cause defenders to panic and run away. But the slow, unreliable tanks could not exploit these breakthroughs.

WWI tanks also suffered from design shortcomings. No one knew what a tank should look like, or what its capabilities should be. Armor was thin, though it would stop most rifle or machine gun bullets. Armament was also light - many tanks had only machine guns, and even those mounting cannon firing explosive shells had very little cannon.

The main problems were technological, and would mostly be solved by the next war.