> they want one.
Polls consistently show less than 50%. Perhaps the "they" you meant is the SNP?
You don't know why the overwhelming majority of them voted as they did. Maybe most of them can't be said to know. It suffices that they voted.
You are free to announce how you will vote, and why. And you can change your mind afterward, and vote the opposite, without telling anybody.
This is all absolutely elementary civics.
The intentions of politicians are not my business and that is "absolutely elementary civics". That isn't credible.
As to the rest, obvious and irrelevant. When did I make any comment on someone else's right or reasons to vote? I didn't, thank for noticing enough that you refrain from attempting to use it to obscure the issue at hand - your claim about what is my business or not.
They can guess reasons why they think voters want it, and some voters may suggest reasons they think will be persuasive. The pols might offer reasons, too, but they don't really know, so you won't really know either.
And, it doesn't matter. You will vote for, against, or abstain, regardless. People can try to persuade you, but they are not obliged to tell you the truth about their own reasons. The pols, anyway, just want to get elected again and hope that supporting or blocking a referendum vote will do that for them. That is their actual reason. but it doesn't help you any.
If you really believe everybody is telling you the real reasons why they do, promote, or block this or that, I have a bridge to sell you.
If it fails, then not enough wanted to leave. That is all.
When they failed to do Brexit for years running, and it turned out the arguments for were lies, there should have been another Brexit vote. It would have failed, and a great deal of trouble would be saved.