At the beginning of the 20th century, the british army massacred the Tibetan army.
A few years later, the predecessor of the Dalai Lama massacred all the christian missionaries and threatened the same to any non-buddhists (mostly non-tibetan chinese) who did not convert.
This is when the state makes a belief the state religion, or even where it is simply the local custom, then people are born into the religion - it does not mean that they adhere to it or follow it.
Also it is really questionable whether tibetan buddhism can be simply called "buddhism" given the huge vedic influences in it - it's a horrifying bundle of superstition for me.
The west has cultivated tibetan buddhism, the present dalai lama receiving funds from the CIA, as part of its Cold War Strategy against China.
For more than two thousand years the state has controlled religion - why does one think it has suddenly stopped? Religion is part of the state, an important tool of the state. It has always been ready to annihilate beliefs which threaten it, especially beliefs controlled from abroad - hence the problem with the Roman Catholics, because the Vatican does get involved in politics and also worked with the CIA.