Question Cameron's decision to impose fundamental constitutional change

Britain is in a political crisis brought about by the transfer of supreme authority from the electorate to the government. It is not true to say that the people decided to leave the EU, because that claim presumes that the electorate has followed the government's instruction that they must make the decision. For the government to instruct the electorate on how to vote & then instruct Parliament on how to interpret that vote is fundamentally undemocratic. Why was that instruction issued?