Why are the best equipped? The exhibits still exist, in great condition and can still be viewed by the public, so they must be doing something correct.

Perhaps what you fail to realise is that a great many treasures have been looted and sold into private collections over the years. Looted and sold by locals, to anyone who can pay. So there is a good chance that anything that the British Museum received as loot would have been someone else's loot otherwise.