Given the context of his negotiations with French President Emmanuel Macron in October which secured the current Withdrawal Treaty, I think the way forward is clearer now.
The Macron Gambit
Germany is dead set against any of these things occurring. It wants to continue with using the euro to underwrite its mercantilism to leverage its industrial prowess. It has benefited handsomely at the hollowing out of member states economies through internal trade advantages. And then, once they were broke used debt restructuring as a bludgeon to buy up their assets at pennies on the euro, c.f. Greece.
The Double Cross
The miserable polling data is a reflection of the economic misery of German austerity taken too far.
So the deal is pretty simple in the end. The collapse of Project Fear to dissuade the British people against Brexit forced a reconsideration on the ruling elite who finally felt a real threat to their power. Because if they betrayed Brexit one of either Farage or Jeremy Corbyn could have entered 10 Downing St. giving real voice to political change in the U.K.
This forced Macron and Johnson to make a deal which gave Johnson just enough room to win the election and blame the Remainers. This ends the stalling and Macron can use Brexit to his advantage within the EU to get what he wants.