Take Control of... borders, laws, money....
It was about bringing power back from Brussels and as the referendum was close, had the EU been more pragmatic with Cameron, they may well have averted it. But I think their arrogant approach to some of his quite sensible requests tipped the balance.
Interestingly now, the borders element is being pushed by Macron and I can imagine he'll get quite a bit of support.
With respect to economic issues, the Remain side produced a load of dodgy information that took some reasonable analysis suggesting a 2-3% lower GDP than if we were to stay in over around 15 years and tried to make it look calamitous.
Project Fear.
Seems that tactic worked with Indy Ref, so they tried again, and we now get it with the Climate Catastrophe and the Covid Pandemic Presentations.
The public generally see through such unwarranted scaremongering.
The graphic above that you posted earlier is just the irrelevant convulsion of a dead corpse of a cause.