"Officially" the King of France wiped them out claiming they were a bunch of Satan-worshipping homosexuals.
The real reason, as has been mentioned, is that they'd gotten too powerful and wealthy. The concentration of wealth they had was really beyond belief.
The King of France wanted their money, so made up some garbage about them worshipping Baphomet.
Some did indeed get away: after all they weren't all in France at the time.
There are well attested Templar sites in Ethopia and (amazingly) the North American continent - including a beacon tower with measurements based upon the scottish rood (sorry can't remember where it is exactly)