Answer:
It began to decline because of its anti-war movement.
Step-by-step explanation:
The Industrial Workers of the World (IWW) was established in 1905 in America by Samuel Gompers.
The Industrial Workers of the World was one of the radical groups that support the anti-war movement in the United States.
When war broke out, the Industrial Workers of the World were the primary target of the government. World War I proved the downfall of the IWW, and it could not resist the governmental attacks the war had supported.