So whats the deal with the SPD winning those clusters of directmandat seats in rural parts of Niedersachsen and Hesse?
The red area in Southern Lower Saxony is where VW and Audi are located. Furthermore, Sigmar Gabriel's and Thomas Oppermann's constituencies lie in that area.
Audi? Seriously?! VW (Wolfsburg) is located to the north-eastern end of the mentioned area. The SPD strength in most of Southern Lower Saxony has nothing to do with it. Gabriel and particularly Oppermann are just two SPD politicians with few effect outside their own constituencies.
(Sorry if that sounds rude but I've read so much hot take analysis on the atlas that sometimes I can get impatient.)
Yes, protestantism (or rather the absence [except for Hildesheim and a small part of the Eichsfeld] of historically SPD-impeding catholicism) plays a role in Northern Hesse, Southern Lower Saxony and neighboring parts of Westfalia and Lippe. One might of course ask why the areas north of Hannover are slightly less SPD-friendly. Well, they're flatter, traditionally less industrial and former strongholds of the (conservative) Guelf loyalists.
(And not everything needs to be compared to the USA. I our case the comparison is also inappropriate because Hannover, Braunschweig, Kassel and Salzgitter are even less conservative than the surrounding.)
Guelfs? As in the pro-Pope faction in Italian medieaval wars?