LONG POST WARNING
This is a question that’s worth addressing because the northern crusades are very overlooked by the middle eastern ones. The environment in every sense of the word was different.
The Teutonic order was first called to Poland by the Duke of Masovia, Konrad I in 1226. Their territories were being raided by Prussian pagan tribes, pillaging and looting and the sort. These tribes regularly engaged in infighting and raids across borders into villages while also conducting documented cases of slavery and human ritual sacrifice.
The Teutonic knights came in at first to stop these raids from happening. Their political ambition pushed them to push further and further into the lands of said tribes mentioned earlier.
Large-scale Prussian raids into neighboring Christian areas were brought to an end, Christianity in the land was more firmly established. They also encouraged settlement and economic development within these lands they ruled over.
The Knights built towns, introduced German law to cities, promoted trade, and integrated the region into Hanseatic networks. The lands were safer, albeit brought by sword.
It was seen as bringing order, religion, and economic growth.
So overall the Teutonic conquest of these lands didn’t suddenly introduce violence to a peaceful society. These lands were already hostile and violent.
Instead they replaced a tribal power balance with a centralized military state that brought order, economic prosperity, a stronger legal system and much more.