Short answers, pulled from the story.
The Stresa Front was a 1935 agreement between France, Italy, and Britain formed to contain German expansion. The alliance began with a four-day conference starting on the 11th of April 1935 in the town of Stresa.
Sir Robert Vansittart drove the creation of this alliance from the British diplomatic corps. His goal was to contain German power through collective action by bringing France, Italy, and Britain together.
The short-lived Front collapsed because Italy invaded Abyssinia in October 1935 completely. Mussolini felt betrayed by the UK signing the Anglo-German Naval Agreement in June 1935 without prior consultation.
Germany declared its intention to build an air force in March 1935 which marked a direct violation of the treaty. The government increased its army size to 36 divisions containing 500,000 men while conscription remained forbidden under the original terms.
Italy held crucial strategic importance for controlling Germany due to its geographic location suited for defense of Austria. Italian forces prevented Nazis from taking power in Vienna during the July Putsch of 1934 by sending four divisions to the border.