I think because of the abundance of expertise in low-level machine language there, many cracked deDRM'd binaries or patched executables for abandonware games come out of Eastern Europe, hence the association.
I remember finding some patches for Heroes III that were only available on some .ru site and there were lots of ads if you turned the adblocker off.
I couldn't read Russian but it was pretty clear they were not the highest quality of ad.
I believe some Americans underestimate how many forums are actually hosted in Eastern Europe. They're still popular over here.
In Norway (~5M population) you'll find atleast 3 huge forums but also several niche ones.
When I wanted to change some hidden settings on my car I found many strange software packages on these strange forums. But nothing on GitHub, these forum people live in their own strange walled of garden.