I've made this point before, based mainly on anecdotes from my unfiltered social media accounts (ie i am 'friends' with all sorts, not just those who agree with my POV) and from conversations during my significant travel round the UK (pre Covid) mainly pursuing my music mag editorship:
Regardless of what the exam question was, most folk I spoke to (who voted leave) did so for one of three reasons, none really to do with our relationship with EU and all intertwined. They were:
Lack of control of immigration - from anywhere. VERY few ever expressed a blanket hatred of the concept of immigration, fewer still a hatred of immigrants as individuals, but the lack of any effective filters was a constant 'top of the pops' in any discussion.
Loss of control, not of sovereignty but of 'Britishness' (and more specifically, because the smaller nations seem more able to resist, Englishness). The idea that 'diversity' is 'good for us' and 'something we need to embrace' is considered a box of *******s by most people, funnily enough the more so the more someone lived in a 'diverse' community (come to Great Yarmouth with me any time with a 'Diversity Rules' badge on if you want a healthy discussion!)
A feeling that 'we the people' are being subject to coercive control by 'the establishment' being told 'what's right' in a manner far more extreme than even the old days of 'doffing one's cap' to the gentry
The 'me' of 2009 would have just laughed all that off, but it was then that I started 'getting out more' (and very much outside my bubble) and had my eyes opened. As I've said 1000 times before I voted remain, and very much from an 'I'm alright Jack' point of view, but I've stuck up for the Brexit result and those who voted thus because I've seen the anger and despair out there that the normal 'man in the street' has been marginalised, and Brexit was seen as a means to punch 'the establishment' on the nose without especially betraying deeply held political leanings
Observation not (necessarily) opinion