Re: no surprise
> Assuming (no evidence to support this, but it's a reasonable hypothesis) that most people that voted for Brexit agreed with the ideals put out at the time of the referendum, and which have been repeated continuously since then, Brexiteers voted to leave the single market and so end free movement.
I'd say your very first assumption is incorrect, and therefore invalidates the rest of your argument.
Many prominent brexiteers said that brexit didn't mean leaving the single market:
Daniel Hannan: "Nobody is talking about leaving the Single Market"
Farage: "Wouldn't it be awful to be like Norway?" (i.e. proposing that we would in fact be like Norway, who are in the Single Market)
Also, your argument is based on people following the logical conclusion of their thinking. Most people don't do that, most of the time.