While I'm happy to agree with NJ that "[Vince Cable] has no idea why any particular section of the electorate voted the way they did and it is presumptuous in the extreme of him to believe that he does", it then seems to me to be presumptuous in the extreme for NJ to go on to explain why *he* thinks the electorate voted the way it did.
It's presumably a given that the 17 million or so Leave voters did so for multiple reasons. Cable will (sadly) have been right for some voters, whether they care to admit it or not; NJ will be right for, I would hope, rather a lot more, but both will have missed reasons all the same.
The best data available at the time, from Lord Ashcroft's Polls, suggests that NJ's reason (sovereignty) was the leading cause to about half of Leave voters, but control over immigration was the second biggest issue (about a third). Even then it's a stretch to suggest that control of immigration automatically equates to "nostalgia for White Britain", or however Cable put it exactly, but that there was a mix of reasons is still clearly intuitively correct.
http://lordashcroftpolls.com/2016/06/how-the-united-kingdom-voted-and-why/