What is China's interest in occupying Tibet?

I would say the one of the primary reasons China occupied
Tibet in the first place was to display to the World the superiority of the newly
created communist regime that had come into power. One has to remember that China broke
all prior treaties which had been created between the rulers of Tibet and those of China
after the communists defeated the nationalists and won the civil war that had started in
China, in 1950.

The reasons for the continuation of Chinese
occupation include the discovery of large deposits of natural resources in Tibet which
include copper, lead, zinc, etc.

The glaciers in Tibet also
form a large resource of water which is essential for China and also acts as a leverage
against India, the largest rival of China. Some of India's most important rivers
originate in the glaciers of Tibet.