ironically strong in eastern Germany
Ironically, no. This goes back to before 1990 (Wall coming down). From end of WW II to 1990....there just weren’t that many migrants in DDR (old East Germany). So this acceptance of migration is mostly a West German thing.
From 1990 to around 2014...they (the ‘Easties’) quietly went along, and when the crisis started up with Syria/Iraq...acceptance in the east wasn’t there. I might add...there’s also more of a anti-US/pro-Russia feeling in the east as well. Unified isn’t what you might think.