I used to come here to get away from Brexit.
I haven’t watched your links yet but will later.
What I do know is that Brexit happened because of the inexorable rise of UKIP. In 2014 they walked away with 24 MEP and 163 local election seats. In the 2015 General Election they received almost 4 million votes (getting only 1 MP, whilst the SNP, with 1.5 million votes, got 56).UKIP were cutting the Conservatives feet out from underneath them and approaching a tipping point, which would vastly increase their numbers in Westminster at Tory expense.
In response Cameron, for the 2015 GE, made a manifesto commitment to hold a referendum on EU membership. That was believed to be the main reason the Conservatives won a small majority. He gambled, knowing he had the full weight of the government and big business machines behind him, expecting to win comfortably. As did almost everybody else, right up to June 24th.
The rest being history.