[Ger-Poland-Volhynia] Reasons for Germans leaving Poland for Volhynia

[Gilbert A Stelter]

Gil Stelter in Guelph, Ontario. This fall I'll be visiting the villages in Poland and Ukraine where my ancestors lived.

But I have a problem with the general story of why Germans left Poland in the 1860s and migrated to Volhynia in such large numbers. My great grandfather, Martin Stelter was born in Janowka, Piotrkow in 1809. His parents must have migrated to that area after the partitions of Poland in the 1790s when it became South Prussia. I don't yet know their names or where they came from. That area of Poland because Russian territory after 1815.

Martin took his family to Volhynia in 1867, part of a large migration. The reasons usually given include the freeing of the serfs and the Polish Uprising of 1863. What is not clear to me is why so many Germans decided to move further into the Russian empire. PArticularly as Russia was doing its best to Russify Volhynia, and was moving against the Polish landlords there. 

What am I missing? Were these people misled about the situation there?
I've been reading Weeks, NAtion and State in LAte Imperial Russia, WAndycz, The LAnds of PArtitioned Poland and others, including Jerry Frank.