I really hope I'm wrong.

Amazing how many unsupported assumptions you can get into one sentence! You do not know how many people voted Conservative because of Brexit, and how many for other reasons (there are some obvious candidates!). Nor do you know how many voted because they wanted what you call a “hard” Brexit. Some probably just wanted any kind of Brexit. Nor do you know that these people think “it’ll make the country better”, whatever that means. Many probably just want to be independent, for better or worse. Some no doubt expect specific policy changes, such as restrictions on immigration. Some probably just wanted to give the left-wing establishment a bloody nose. Some (including, I know for a fact, some who personally supported remain) simply take the view that if you promise to do something you should do it.

As to thatcherite economics, Johnson has promised more borrowing and more government spending, especially on capital projects. Nothing very thatcherite about that.