You have literally no idea of what's going on in Germany as a result of Merkel's decision, do you? A nation that had no terrorism problem has now imported one; it has lost roughly half a million of these migrants and has literally no idea where they now are;most of them are unemployed and a massive burden on the resources and infrastructure of the country; the country is suffering a spike in violent crime - particularly sex crime - that is unprecedented in its history and every town centre is full of hordes of middle Eastern/North African men in large, intimidating groups; and, of course, having taking this monumentally stupid step unilaterally, Germany has tried to force other EU states to take some of these people. Understandably, many have told them to fùck off and sort out their own mess.
That's why millions of people are suddenly voting for the only party on the ticket that actually acknowledges that there's a problem - let alone plans to do do anything about it. Merkel's idiocy made this election result happen. If you think that gives her or Germany any moral superiority, you're deluded. As for the whole thing being a 'net gain', the idea is laughable. Even Merkel has admitted she regrets it, ffs!
And we've established already that you have barely even the most rudimentary idea of what Brexit is, what it actually means or the reasons behind it, so kindly forbear from pontificating on the subject.