BY WAY OF POWERLINE: Why hasn't Brexit happened yet? Here's the gist:

Brexit showed that, for elites to whom the European Union offers a grand role, that moment has come already. The European Union, not Britain, is their country. They saw Brexit not as most British people did—as a solemn and even sacred uprising by an ancient people against a usurper. No. Elites saw Brexit as a local nuisance in the domestic politics of the only legitimate custodian of Britain’s long-term interests: the European Union.

It's a long article, but well worth the read if you want fully understand Brexit. It's also useful in understanding the current Democrat meltdown; the same premise applies.