Italy helps but honestly the biggest factor is keeping france from violating Belgian neutrality, once the british empire joined the war it was over for the Entente.
The British were bound to join the war. By joining the Central Powers side, they could undermine the Germans at the peace talks and prevent their domination of the continent and limit their potential colonial gains at French expense.
And once Britain joined the Alliance, Italy, Japan, Ethiopia, and Siam followed suit.
The Italians made out like bandits but were still dissatisfied. One would think that Nice, Savoy, Corsica, Chad, Ubangi-Shari, and a slice of Egyptian desert and Algerian desert would have been enough for them. They wanted Tunisia, but Britain insisted on an independent Tunisia as they didn't want the Italians controlling both sides of the Strait of Sicily - this angered Italy and they called it a stab in the back. They were similarly angry about Djibouti going to Ethiopia. Nevermind how much value they ultimately got
Japan fared well. North Sakhalin and Russian Manchuria were worthwhile prizes. If they didn't have to expend all the effort to protect those territories from the reds, the Japanese might have attempted to expand elsewhere - probably Chinese Manchuria.
Britain set the stage for much of 20th Century decolonization though. By establishing quasi-independent polities in Morocco, Algeria, Tunisia, Vietnam, Laos, and Cambodia - it set a precedent that'd be followed as decolonization came along.