Why did President Wilson believe it was necessary to put so much energy and so many resources into propaganda and quieting dissent?

In order to support his decision to go to war with Germany.

Explanation:

Back in April 1917, President Wilson created a committee to change perception and popular opinion through influence media.

When the Woodrow Wilson wanted to go to war with Germany in April 1917, he faced the challenge of reluctance from the people because he had won his reelection in 1916 based on the fact that it was believed by Americans that "He kept us out of the war."

However in desperation to convince Americans that going to war with Europe was a necessity, the Committee on Public Information (CPI) was created.