The family history says that Emilia and Peter Griebel knew each other in Germany, but given the distances between their birthplaces (over 1000 km) and the political situation, this seems unlikely.
The most likely reason they left Germany was that Napoleon III had declared war on Prussia on July 19, 1870 (see Griebel Family). It would therefore seem likely that they were fleeing the war and mobilisation (Germany delivered 380,000 troops to the forward zone within 18 days of the start of mobilization on July 14).
They must have known the Ellenbergers from the same town (see below), who had emigrated to New Zealand in 1863. It would seem likely that they followed them to New Zealand. A further attraction may have been the Vogel Scheme, which started in early 1870.