East Germans are a lot poorer, the East German economy is a lot lower productivity and investment, and politically the old DDR states lean a bit more right (ripe area for AfD recruitment).
Some West germans still look down on Ossies, even though Merkel was one herself. It's a lot like how northern states look down on southern states in the U.S.
Interestingly enough, the east is the most prolific voting area for both far right and the left. Both AfD and Die Linke had their best results in the eastern states.
Might be connected to the horseshoe theory, I'm thinking. Where voters don't have a specific connection to any one political mindset so they choose the party that is the most extreme in their mind and won't hesitate to switch to another more extreme party, even if they switch from far left to far right because they aren't affiliated with a specific political mindset.
Some West germans still look down on Ossies, even though Merkel was one herself. It's a lot like how northern states look down on southern states in the U.S.