Why is a mixture of hydrogen and oxygen especially dangerous in a 2-to-1 ratio?

A mixture of hydrogen and oxygen in a 2-to-1 ratio is especially violent because it represents the stoichiometric proportion required for the complete chemical reaction between these two elements to form water, as expressed by the equation $2H_2+O_2\to 2H_{2}O$.1

In this specific ratio, the reactants are perfectly balanced to consume one another entirely, leading to a rapid and highly energetic release of energy when ignited by a spark, flame, or catalyst. While mixtures containing between 4 and 94 percent hydrogen are flammable when heated to 550°–600° C, the 2:1 mixture is particularly dangerous because it maximizes the efficiency of the combustion process. The reaction itself proceeds through complex branched-chain mechanisms involving the interaction of atoms and molecules to produce hydroxyl radicals, ultimately resulting in the formation of water.12