The only astonishing thing about this vote is that it ever took place.
It was Cameron's way of trying to get re-elected in 2015.
He announced in January 2013 that he would hold an EU referendum if he is re-elected in the 2015 election, knowing how popular an EU referendum was amongst the people. He did it to try and win votes - and thought he needn't worry about holding it should he win the 2015 election because there was no way the people would vote to leave the EU.
So he won the 2015 election, stuck to his promise and brought about the 2015 European Union Referendum Act. He duly held the referendum on 23rd June 2016, in which the British people, rather gloriously, defied the Cameron Government, Obama, Lagarde, Carney and daft warning of WWIII and deaths of all firstborns by voting to leave the European Union.
As a result, Cameron lost his job and Britain regained her sovereignty and the pro-Eu British and world establishment was given a good punch in the teeth...