(a) The number of intentional leaks in Microsoft products (esp new Window's) that might be inspired by NSA surveillance
(b) The leaks showing German BND and Five Eyes cooperate very closely on SIGINT with BND letting them use selectors that no patriot of German government or industry should've tolerated.
Many articles, esp Der Spiegel, also indicate that German intelligence is lap-dogging so hard in an attempt to join Five Eyes club. Additionally, remember that the TAREX teams in ECI leaks were focusing on Germany, South Korea, and China. Yeah, not all the terrorism they talk about on TV: one opponent and two seeming partners. What do all three have in common? They're among the biggest economies competing with American (and Five Eyes') business interests. Makes sense among scheming intelligence agencies to use assets against them to get privileged few tight with Washington a competitive advantage and do counter-intelligence against their agencies doing the same.
So, Microsoft are either a bunch of idiots that have no awareness of Snowden leaks or reporting on the situation with NSA and Germany. Or they knew that while subverting their European offering to give NSA every chance to hit the customers' data as a favor to them to avoid pressure and keep lucrative contracts. I'm betting on the latter to be safe and continuing a boycott of Microsoft tech where possible.