I can appreciate that if, as an MP, I honestly think that leaving will damage the economy and is against the best wishes of my constituents then I may vote against Brexit despite the referendum.
However, we had a general election following the referendum and MP's wishing to take this stance needed to make it clear to their constituents that this was their view so as to give the electorate the choice to oust them for it. The fact most of them will have kept the view to themselves during the election even though they must have already formed it at that stage is at best self serving and at worst downright deceitful.