Without having done the research ...
My first guess is that the price leader on this route is one of the Gulf carriers or maybe Turkish. (OK, maybe there's a junk carrier which is cheaper ...)
Lufthansa, and AF/KL and others, will be tracking the fares of all their competitors. When they find the lead low fare, it's up to them to decide whether to match/beat it or not. Bear in mind that their head office will be on the back of their UK sales manager 'why aren't you meeting your targets?' and he'll be replying 'because Emirates are stealing our lunch - we have to match them or give up the business'.