Why did Italy start fighting in the Second World War as late as October 1940?

The Second World War broke out in September 1939 following Adolf Hitler's invasion of Poland. Fascist Italy and Nazi Germany were allies, and had been since the Pact of Steel in May 1939. As a result, Italy was obliged to enter the war at the same time as Germany. However, the Italian economy was weak and Italy did not have the resources to fight a war. Thus, Italy was in the war for over a year as a 'non-belligerent,' that is to say, a party who does not fight. It was not until October 1940 that Italy became militarily involved in the war, when it declared war on Greece. Even when Italy fully joined the war, the Italian army was poorly organised and underfinanced. It was simply the case that Benito Mussolini, the Italian Prime Minister, and his government knew that they could not evade fighting in the war any longer, due to their alliance with Nazi Germany.