The former DDR is actually shockingly visible in a lot of maps of Germany. Electoral voting preferences (especially looking at AfD, die Grunen, and die Linke), various economic indicators, average size of farms, vaccine rates (data I'm seeing is from 2009, may or may not still be true today. This is actually one of the few indicators where the east wins), religion (particularly non-Christian).

This article shows a bunch of factors.

As does this video.

That could easily be the result of poor geolocation of residents (we know you're in the country but we can't narrow this down to a zip code).

Also, not clear at all how many of these accounts are bots. A country saturated with the equivalent of online phone banks could easily tip the scales one way or another simply based on how they invent/associate accounts.

To my knowledge (as someone from former West Germany), East Germany was ahead with incorporating women into the job market. Presumably, that is still the case. So, it could be that the friendships came to be from working together as colleagues...

That may just be the cause then? The difference in relative population? Since we don't know from the graphic what the numerical foundation is, it might be sometime that skews toward the "more common" side when there's just less women in an area.

You can even get it within a single city. Sydney's "Red Rooster line" is a well-known example here in Aus.