Why did the 14th Dalai Lama become Tibet’s head of state at age 15?

The 14th Dalai Lama assumed the role of head of state at age 15 due to a looming political crisis caused by the arrival of Chinese cadres in Tibet in 1950, following the Chinese Communist Party's rise to power in 1949.1

Although the Dalai Lama would typically have assumed control at approximately age 20, the escalating threat to Tibet's sovereignty necessitated his early transition to full power. He was formally vested with these responsibilities on November 17, 1950, in an effort to protect the interests of the Tibetan people during a period of significant instability and military intervention by the People’s Liberation Army.123