A higher turnout than the referendum in 1975 (64.62%) to stay in... Does that mean it was never the will of people to be in (then) EC at all?

Of course it was the will of the people. Those who didn't bother to cast their vote didn't get a say.

The rest of the people knew about this vote and they didn't care enough to vote. What are we supposed to do about that? Should we force everybody to vote?