For the POTUS elections, trump lost on a count of just shy of 2.9million votes, but won by the electoral college.
By applying that logic to the brexit referendum, breaking up over the 5 countries that voted (england, scotland, NI, wales, gibralter) remain would have won. By dividing up the 382 counting areas [0] I'm sure you get a different result too.
For a UK parliament vote, I'm not sure on what the result would be if you took a voter turnout by percentage across the countries, and then evenly distributed the MPs based on those number of votes, but I'm sure someone has done the analysis somewhere.
To go back on topic, my point was (supposed to be) more about how a tyranny of the majority can happen, and does happen, in western countries (with some slightly alternative points such as the fact that majorities aren't always majorities)
[0] https://www.electoralcommission.org.uk/find-information-by-s...
Well, that's how referendums work, there is never 100% turnout. So the amount of people who votes constitute the "100%" and you only need 51% of that to win a referendum.
Your argument is also not good because by following your logic we could say that almost no US president has ever gotten elected by majority, at least from top of my head I am not aware of anybody actually being elected by getting votes of 51% or more of all eligible voters.