Why did the Entente betray Italy after WW1?

The Entente allegedly betrayed Italy after WW1 due to several reasons: the collapse of Austria-Hungary, the rise of Yugoslavism, France's desire to expand its influence in the region, and the United States' belief in self-determination. The Treaty of London, which promised Italy certain territories, was no longer feasible due to these changes. This led to Italy receiving less than what was initially promised, causing resentment towards Britain, France, and the US.

via Why did the Entente betray Italy after WW1? (Animated History Documentary)