The violence has a long history,
"In 1193, the Nalanda University complex was destroyed by Afghan Khilji-Ghilzai Muslims under Bakhtiyar Khalji; this event is seen as the final milestone in the decline of Buddhism in India." http://en.wikipedia.org/wiki/Muslim_con ... bcontinent
The question is rather why the violence has escalated now?
This is a part of larger tragedy. Bangladesh is prone to floods, and now, with the advent of global climate change, these floods have risen to unprecedented levels.
"In 1998, over 75% of the total area of the country was flooded. It was similar to the catastrophic flood of 1988 in terms of the extent of the flooding. A combination of heavy rainfall within and outside the country and synchronization of peak flows of the major rivers contributed to the river.
The 2004 flood was very similar to the 1988 and 1998 floods with two thirds of the country under water."http://en.wikipedia.org/wiki/Floods_in_Bangladesh
Since the key countries emitting CO2 - USA and China - still don't act on this issue, the floods will get even larger, which will lead to more illegal immigration to Myanmar (which has uncontrolled border sections), and to more ethnic tensions.