Interesting. My recollections and impressions are that Britain was always a somewhat hesitant and reluctant member of the union, embracing association, but hesitant with respect to the "ever close union" postulate it included, That clearly was a factor (probably along with long term memories of the "sterling zone" in their decision to reject the Euro as their currency (as did some other EU members).
I'm not sure I accept your "jumping off a cliff" metaphor. The UK survived and prospered for a very long time on the other side of that cliff: the situation now is, of course, different in that almost all of her her European neighbors are now part of the EU, however, the UK has an history of economic relations all over the world, as, of course also does the EU.
I don't claim detailed knowledge of the process leading up to the Brexit vote (or of the various ratios of votes cast). I'm aware there was vigorous campaigning on both sides of this issue, and that it, and other EU issues, had been a part of the ongoing UK political debate for some time before PM Cameron put the issue before the voters ( expecting, it appears, a rejection by them).
By law,he British Parliament is the ultimate authority on such issues, and is empowered to overturn the previous vote. I'm not aware of any effort on their part to do this or even conduct another referendum. I suppose either is still possible and don't know the likelihoods involved.
Brexit was a political issue in the UK long before Trump entered the political scene. I recognize that Trump is the contemporary American boogey man in the European political scene, however there is no direct connection. I do believe that there are likely a few common factors behind public support for opposition parties ( and some in office) across Western Democracies, from Poland, to Hungary, France, the Low Countries and across the Southern Tier of the EU, however there is no organized conspiracy, if that is your point. Indeed many of the issues that appeared to motivate the Brexit vote in the UK also appear in the rhetoric in these other EU countries. They are all democracies and it is no surprise that such debates occur.