Not well known but this was actually the second Brexit referendum. The original decision to join the EU wasn't decided by a referendum at all, a Labour government just did it, despite the profound constitutional implications. So there was no argument for requiring a higher threshold to leave than the join. Arguably leaving would not have required a referendum at all, given that joining didn't.
But when people cried foul about this move in 1973, Labour agreed to hold a referendum on leaving it again, which was held in 1975 and won by Remain. Unfortunately, the way they won was by misleading the public. They claimed the European Economic Community (as it was known at the time) was purely about building a free trade zone, with no political unification goals. Official leaflets sent to households said no federal "United States of Europe" was intended. The Leave campaign pointed out that it wasn't true and the EEC wanted to take over political power in Europe.
The Leave campaign were honest. The EEC later rebranded to the EU, and took over many powers that had nothing to do with free trade. This is one reason why a common comment heard from older people back in 2016 was "I voted Remain in 1975 and I'm voting Leave now, for the same reasons".
Regardless of the legitimacy of your other arguments this is a silly thing to say.
Besides the lies and misinformation. Boris was driven purely by his political ambitions and saw Brexit as a great opportunity to take over the Conservative party. That’s it.
Also legally binding referendums are not a thing in the UK. They aren’t a requirement for anything and the parliament has the right to do whatever it wants. Of course it would be a political suicide to ignore the outcome when you agreed to hold one.
Of course tying it to turnout would have been a sensical idea (i.e. requiring that at least 50% of registered voters would vote for leave for it to be binding)
But when people cried foul about this move in 1973, Labour agreed to hold a referendum on leaving it again, which was held in 1975 and won by Remain. Unfortunately, the way they won was by misleading the public. They claimed the European Economic Community (as it was known at the time) was purely about building a free trade zone, with no political unification goals. Official leaflets sent to households said no federal "United States of Europe" was intended. The Leave campaign pointed out that it wasn't true and the EEC wanted to take over political power in Europe.
The Leave campaign were honest. The EEC later rebranded to the EU, and took over many powers that had nothing to do with free trade. This is one reason why a common comment heard from older people back in 2016 was "I voted Remain in 1975 and I'm voting Leave now, for the same reasons".