In my home town, there was a German fellow who immigrated to Canada in the 1950s. He was a teenage soldier on the Channel Islands and stayed there for the entire occupation.

His take was that there was an uneasy truce between the residents and the soldiers. If the residents kept the soldiers fed and housed and offered no rebellion, no military action would entail. Both sides were patiently waiting for the war to end.

But he might have seen things through tinted glasses. There were some atrocities, as this article suggests. Another article on Medium went into more detail.

My brother-in-law's father lived through the Nazi occupation in Holland. He had some really bad stories to tell. It seems the Dutch got it worse than the Channel Islanders.