Be fair, Benes didn't have much say, England and France basically pushed him out of the way in Munich.
Benes had an army to do his talking for him. He didn't have to involve Britain and France. Historians blame Britain and France, but it was a weak-kneed Benes that allowed them to dictate terms. Czechoslovakia had a pre-war population of 15m (triple Switzerland's) and a thriving arms industry. Note that the Swiss did not ask Britain and France for their opinion about whether to submit to Germany. Czechoslovakia had hundreds of thousands of Jews who could probably have been relied on to fight to the death. It could have declared itself a sanctuary for Jews, contingent on military service by a male member of the family. Bottom line is that Benes wimped out, and the nation suffered the consequences.