It happened at all because the UK was the most Eurosceptic big EU country so it could still have an impact on the numbers.

Also, negative and positive feelings are not the same thing as a vote. For example, some people who felt negative about the EU voted remain because they were worried about economic disruption (the government was predicting a severe recession in the event of a leave vote - not after leaving, merely as a result of a vote). I am sure people can think of other examples and both ways, but the point is that "feel negative/positive" and "would vote to leave/remain) are not the same number).