I probably should have emphasized the "partly". Of course, other factors also played a role in its demise, but they did try to gain footing in other European countries rather late.

Concerning Xing: Yes, you're right, this went very differently. It would be interesting to compare the LinkedIn/Xing and Facebook/StudiVZ situations to find out the differences and commonalities, but to do so in detail is beyond the scope of a comment, I think.