Bombardier is French. And of all the things the French despise, the Germans are very high on the list.
Siemens is German and of all the things the Germans hate, the French are very high on the list.
And many customers, among which the Dutch railway company Prorail for which I have worked, prefers to buy material from as many different vendors as possible, to prevent vendor lock-in.
So the company that made the TGV and holds the world speed record for rail with it, and the company that made the ICE, the most comfortable high speed rail in the world, will not be working together soon.