The East was never really invested into after reunification
Gee, I wonder why, after having been screwed by the sovjiet regime for decades (first by complete destruction of all industry, then in regards to fair voting process) and then getting screwed by west Germany by complete destruction of all industry & a lot of scams running wild, thus leading to high unemployment, thus leading to all kind of fun things, like widespread drug abuse, which then leads to domestic abuse and poorer education, digging the hole even deeper.
This is a problem 75 years in the making and there is no help in sight.