I'm open to being convined otherwise, but I don't personally think the Cambridge Analytica thing is a big deal. As far as I can see it was mostly a bunch of self-important privately-educated chancers vastly over-hyping their own capabilities. They _want_ to be seen as Bond villains, but they aren't up to the job. Listening to their overblown claims they sounded like a Harley Street quack selling hair transplants or boob implants (exactly the same accent and tone of voice those types use, as well).
There do seem to have been some shennanigans over breaching spending limits, but above all I think the whole exercise was stupid, because those who voted 'for Brexit' never really told the rest of us exactly what they were voting for.
_Now_ the most vocal of them say they always meant 'no-deal Brexit', while others still insist they wanted a better deal but they were betrayed by the cunning remainer May (echoes of the traditional 'stab in the back' myth, as used by the German military in post-WW1 Germany - note how all the Tory Brexiters ran a mile when the time came to actually take responsibility for putting the plan into practice, almost certainly because they didn't have a clue how to do it).
While still others admit they didn't know what they were voting for and wouldn't have voted for it had they known the details, or were just generally pissed-off.
But I'm mostly filled with a feeling of doom either way. Brexit is far from the EU's only crisis, even if by a miracle the vote was reversed we'd just be jumping out of one bitter fight with everyone angry with each other into another, bigger, one. Slower-moving but still with potential disaster round the corner.
I don't buy the more conspiracy-leaning explanations, they all seem too contingent and superficial to me, I think there are deeper trends involved.
I'm not saying it's purely 'economic anxiety', but the loss of belief in collective projects and identites, and the common good, that came with the death of socialism, has left people feeling far more inclined to see life as a zero-sum game and to see all outsiders as potential threats and competitors.