You've got it wrong: "After the deal had been approved, Cameron described it as giving the United Kingdom "special status within the European Union" and immediately declared that both he and the UK Government would campaign for a "Remain" vote in the referendum within a "reformed European Union"." https://en.wikipedia.org/wiki/2015%E2%80%932016_United_Kingd...

This is was about immigration. I don’t understand why people are still in denial about this. I am pretty sure it would have happened anyway regardless of what economic concessions UK would have got. It’s worth to note that the immigration is still an issue in the UK and the EU and I think more EU members will leave because of this.

The referendum was triggered by him making a bad political calculation that he would win it and could squash the aisle of his party that was pushing his idea. This was never truly due to a failed negotiation. The hardliners in his party wanted entirely out either way.

The referendum was entirely the UK's choice and had nothing to do with the EU. It offered more concessions than the UK deserved (having already held numerous opt-outs) and they still called the vote.

One of the effects of Brexit is that EU popular solidarity has noticeably improved while the UK has gone in the opposite direction. That says a lot about Brexit.